Importance of Natural Resources

Islands: Natural Laboratories of Evolution

It’s my great pleasure to
introduce Jonathan Losos, who is the Monique and Philip
Lehner Professor for the Study of Latin America in the
Department of Organismic and Evolutionary
Biology here at Harvard. He’s also the curator
in herpetology for Harvard’s Museum of
Comparative Zoology, which forms the basis for
our exhibit upstairs and many other of our
exhibits at the Harvard Museum of Natural History. As head of the Losos
Lab at Harvard, his research speciality is the
behavioral and evolutionary ecology of lizards with a
focus on how lizards interact with their environments and
how they have diversified evolutionarily. And the lab primarily
studies the evolution of Caribbean Anolis lizards. Before joining the
Harvard faculty in 2006, Jonathan spent
more than a decade at Washington University serving
as a member of the faculty, the chair of their
environmental studies program, and director of the
Tyson Research Center, helping lead efforts
to provide a living landscape for environmental
research and education at that university. He has received numerous
honors and awards, including nomination as a Fellow of
the American Academy of Arts and Sciences, the Daniel Giraud
Elliott Medal from the National Academy of Sciences,
which honors meritorious work in
zoology or paleontology, a John Simon
Guggenheim Fellowship awarded to those who
have demonstrated an exceptional capacity for
scholarship and creativity in the arts and sciences,
and the EO Wilson Naturalist Award from the American Society
of Naturalists– all of this, in addition to a staggering
number of high-level grants from organizations like the
National Science Foundation. He is the author of the book
Lizards in an Evolutionary Tree– Ecology and
Adaptive Radiation of Anoles, published
by the University of California Press in 2009. And he has also
edited and co-authored other seminal works,
including The Princeton Guide to Evolution and The
Princeton Guide to Ecology. And his work has
been featured widely in the populist
sphere in journals like Natural History, Scientific
American, and The New York Times. A lot of accomplishments–
my favorite is the shirt that he’s
wearing this evening and also the wonderful music that he
DJed for us at the beginning. But please, let me– all–
welcome Jonathan Losos. [APPLAUSE] Well, it’s a great honor to
be talking to you tonight to celebrate the opening
of this exhibition. I just went through it this
afternoon for the first time, and it is simply spectacular. The museum staff have
done a wonderful job, and you’re really going to
enjoy the exhibit that they’ve put together. This is particularly a
joyful occasion for me because I’ve spent my
entire life studying islands and how species have
evolved on islands. And so to have an
exhibit like this and to get to talk about
it is really a lot of fun. As Jane said, there’s
so much to talk about or to put on a display
about island evolution, it was very hard to decide what
to put in and what to put out. And I’ve probably packed
in too much into this talk. But I want to give you a
feel for the diversity that occurs on islands and
how that has informed our understanding of evolution. And one message I want to
make sure you take away from this talk is
that I study islands and many of my
colleagues study islands not because we’re interested
in an evolution in islands, per se. We are, but really
we study islands because they are a
particularly good place to understand the evolutionary
process in general. And so by going to
islands, we can learn a lot about how evolution works. And of course, Charles Darwin
was the first person who really took advantage of that. And a long line of
distinguished biologists have done so ever since. So let’s get right into it. And let’s talk about what
is so special about islands? Why do we evolutionary
biologists love to work there? Well, there are a
number of reasons. First is that many islands
are created as blank slates. They’re volcanic islands
that emerge out of the sea. Not all islands,
but many of them are the result of volcanic
activity underwater. The volcano starts erupting. It puts out lava. It builds up. Eventually, the
lava gets big enough that it emerges out of the sea. And that’s how many
new islands are formed. Now of course, such islands
initially have nothing on them. They’re just molten lava
that cools down into rock. But over time, first some
plants arrive there and then some animals, and an
ecosystem builds up. And what’s so special
about these islands is that each one is
an independent theater of evolution. And you can study that island. And you know everything
there is a result of what happened right there. The species got there,
and then they evolved. And so we can really see
the evolutionary process in very stark detail
on these islands. Moreover, this is
aided by the fact that many types of
plants and animals are not good colonizers, and
they do not get to islands. And this has two consequences. First, the number of
species on islands, particularly isolated islands,
is often relatively small. There aren’t that
many species there. And that makes it
relatively easy to understand how
evolution has worked. I mean, imagine working
somewhere like the Amazon rain forest, where there
are all these species. It’s really hard
to figure out how one species affects another–
what the important factors are. But on islands with
relatively few species, it’s much, much easier to
isolate what is going on there. Moreover, because islands
don’t have that many species, that gives a lot of room for
the species that are there to adapt to new circumstances. And so evolution is really
magnified on islands. It’s much exaggerated. It’s much easier to
see what’s going on. And for that reason,
islands are particularly good places to study evolution. Now in addition, many
islands are young. Not all of them,
but many are young. And that means that the
evolution that occurred there occurred relatively recently. We’re not trying to figure out
what happened tens of millions of years ago. It’s something that
happened geologically in a much more recent past. And thus, it makes it
easier to decipher. Islands also have
defined boundaries. We don’t need to
worry that what we’re studying, that the key
factor happened somewhere else that we’re not looking at. We know what the area is
that we need to study. Now, this is a good
place to point out that my talk today is going to
focus about oceanic islands– islands in the ocean. But the same phenomen that
go on on these islands pertain to other areas
that are surrounded by inhospitable media. For example, lakes
in continents serve as islands for the animals
that live in those lakes because it’s very difficult
for them to get from one lake to another. And so for fish and
other aquatic animals, lakes are essentially islands. Alpine mountain tops also
can serve as mountains. And many people study the island
mountains, they refer to them. Even the human
body can be thought of as an island for the
microbes that call us home. And that’s something
that the exhibit will explore in future days. And so what I’m talking about
really has broad applicability. Finally, perhaps
not most importantly but very importantly,
there are lots of islands. And that allows us to
study what’s going on in many different places. For this reason,
islands have been referred to sometimes
as nature’s test tubes of evolution. Just like a laboratory scientist
doesn’t do his experiment in a single test tube
but in many test tubes to look to be able to tell
what is general from what is a unique happening
in one place, we can look at many
different islands to get what’s generally
important and goes on, as opposed to what
happens in a single place. Finally, islands serve as
alternative evolutionary worlds. They let us see
the different ways that evolution can occur–
the many different outcomes that evolution can produce. By looking at islands across
the range of different islands that occur, we can
get an idea of what evolution is capable of doing. So these are the reasons
that we evolutionary biologists like
to study islands, and we’ve learned
a lot from them. Now in my talk today, I’m going
to focus on three questions. The first question is
who gets to islands? Who are the actual
players that get there? Second, what happens
once they get there? And finally, third, is evolution
on islands predictable? So let’s start with the first
question– who gets to islands? Well, there are a number of
ways to colonize an island. The first is by air. Species that can fly have it a
lot easier to get to islands. And for that reason,
it’s not surprising that birds are usually the most
abundant type of vertebrate on islands in terms
of number of species. They just fly out there. There are other ways of
getting there by air, as well as active flight. For example, those of you
who remember Charlotte’s Web, you remember what spiders do. Baby spiders shoot out
a little bit of silk that gets caught in the wind. It picks them up, and they
can travel great distances in this way. They are sometimes referred
to as aerial plankton. And in fact, spiders are one of
the best colonists of islands. They can travel
sometimes hundreds, even thousands of miles. Plants do the same thing–
at least some plants. They send their seeds
through the air. And these seeds can travel great
distances and colonize islands. So one route to getting
to islands is by air. Another route is by sea. Obviously, animals that can
swim have a big advantage in colonizing islands–
animals, of course, like sea lions and
other pinnipeds. And in fact, sea
lions are usually one of the two types of
mammals that you always find on islands, the other
ones being, of course, bats. Bats and sea lions are very
good at getting to islands. There are other
species, however, that you wouldn’t expect
would be good swimmers but actually are. For example, does
anyone recognize this? Yes. What is it? It’s an elephant’s trunk. At least it was surprising to
me that elephants are really good swimmers. And they actually can
swim great distances. And as a result,
elephants are quite good at colonizing islands. They’ve been know to
swim as much as 20 miles across open water. [LAUGHTER] So elephants are good swimmers. Another animal that to me was
surprising in their ability to cross water are
giant tortoises. Now they don’t
swim, but they have a life jacket on their backs. Basically, their shell is
full of air, and they float. And the reason that we see
giant tortoises on many islands is that they’re able to cross
large distances of ocean. Now this was actually
demonstrated very clearly about a decade ago when
a tortoise washed ashore on the coast of Tanzania. This was a tortoise from
the island of Aldabra right here in the Indian Ocean. It’s an Aldabra giant tortoise. And it showed up here
in Tanzania, a distance of more than 300 miles. Now if you look
carefully, you can see there are these white
things on the tortoise’s leg and shell. Those are barnacles. Barnacle specialists say
that for those barnacles to get that big,
the tortoise had to be in the water for
at least six weeks. And it just floated across. And when it showed up, it
was a little dehydrated. But it wasn’t in
that bad health. And so tortoises are able
to float to get to islands. And that’s why you
find them– or you used to find them– on many islands. So getting there
by air or by sea are two good ways of
getting to islands. But of course, there
are many species that neither fly or swim very
well, and they can’t float. And how are they going
to get to islands? Well, there’s a third method by
which species colonize islands. And that’s by doing
what we call rafting. And it’s just what
it sounds like. It turns out that
the ocean often has mats of vegetation
just floating in it. And animals can get on
these mats of vegetation. They probably don’t
do it intentionally. But they drift along
and get to an island. Now these mats of vegetation
occur for many reasons. For example, this is a
photograph in the Amazon River where such vegetation
mats are quite common. If you go to the Amazon,
you’ll see something like this. And they form in
a couple of ways. One way is just vegetation falls
into the river for whatever reason. And it just tends
to glom together to form a pile of vegetation. Sometimes, however, the
riverbank collapses. It gets undercut by
erosion, and it just all falls into the water and
sometimes with the trees still standing up. And it just goes
floating down the river. And it goes out into
the Caribbean Sea and goes floating along. Well, sometimes
there are animals on these mats of vegetation. That’s a bird. It could fly there. You can see down here. But here’s a raft– of
small raft in India. For some reason, these two
little deer were on the raft. They were probably in the
water, and they climbed there for safety. Now this is not a good
way to get around. Most rafts sink
eventually, or the animals die of exposure or starvation. But every once in awhile,
a raft will actually wash ashore sometime. It’s a very improbable event. But given millions of
years, it does happen. And that’s how many animals have
been able to colonize islands. For example, South American
monkeys almost surely rafted to South
America from Africa. It’s very clear that the
monkeys in South America are African in origin. And there’s really
no other explanation to how they got there. Rafting– it makes
a lot of sense. It’s really the only
explanation, in many cases. But of course, it’s
very hard to observe. And some people are skeptical
that it occurs for that reason. However, there was
a great example of rafting that was documented
a few years ago involving this animal, the green iguana. Now you may be
familiar with iguanas because they are very common
in Central America and South America. But they also occur
in the Caribbean. And they’re very
common, particularly on some of these islands in the
middle of the Lesser Antilles. The islands to the north often
don’t have green iguanas. And this island
here, Anguilla– it’s a British-controlled island–
does not have green iguanas. Or at least it didn’t used
to have green iguanas. But one day, a bunch of
Anguillans were on the beach. And they looked out,
and they saw a mat of vegetation washing ashore. This wasn’t it but
something like this. Now this isn’t that
unusual an event. These things would be out
there, and occasionally they’d wash ashore. What was unusual about
this mat is that it had 15 green iguanas on it. As they watched, the vegetation
washed up onto the beach. And the iguanas just
stepped right down and made themselves at home. And in fact, they’ve
started breeding and have bred prolifically. And now green iguanas, I’m
told, are all over Anguilla. Very clearly an
example of a species rafting to colonize
a new island. Now you might ask, where
did these iguanas come from? That can often be very
difficult to determine. Normally, what we might do is we
might take some genetic samples from the green iguanas and
then go around the Caribbean and take samples from
natural populations to look for a genetic match. In this case, however,
that was not necessary because in the mat
of vegetation, which was a bunch of
leaves and branches and some fallen-over trees,
as well as the vegetation, there were some street signs. [LAUGHTER] And the street signs
were in French. And so that
basically got it down to either Guadalupe
or Martinique. It turns out that three
weeks earlier, two hurricanes had passed over Guadalupe in
the direction of Anguilla. And it turns out
these green iguanas, that’s where they were from. They were from Guadalupe– so
a clear example of colonization over more than 100 miles. All right. So that’s how species can
colonize isolated islands. But another question– we talked
about who’s good at colonizing. Who is bad at colonizing? What are the species that have
difficulty getting to islands? Well, of course, species–
oops, I got ahead of myself– species that don’t
fly or swim very well are going to have
troubles for starters because they have to raft. And rafting is not easy. Among those, amphibians
have particular trouble because as you know, amphibians
generally have moist skin, and as a result, they
dehydrate very quickly. And so they’re not
very good at rafting. And in fact many islands have
no amphibians whatsoever. Species with high
metabolic rates don’t do very well rafting
because basically they burn up all their
stores very quickly, and they starve to death. And by species with
high metabolic rates, I mean mammals. Warm-blooded
animals like us just don’t last very long on a raft. And many islands also
don’t have any mammals. Big species often
don’t do very well, in part because they
don’t fit on rafts. It’s hard for them
to raft along. They also have high
metabolic rates often. And so they don’t
often do very well. For the same reason carnivores
are not very good rafters. And by carnivores I mean
mammalian carnivores. And they are often
absent from many islands. Forest species aren’t very
good because forest species are often adapted to the
cool, moist forest interior. And the hot arid sun on a raft
just doesn’t suit them well. And they can’t survive. Species that have very specific
diets often land on an island, and what they eat isn’t there. So species that are very
specialized in what they eat are not good colonizers. And finally in the botanical
realm, species with big seeds don’t colonize very well
because big seeds usually don’t disperse very far. And what I’m particularly
referring to here is trees. Most trees are lousy dispersers. They can’t get their
seeds very far, and so the seeds don’t
make it out to islands. And for that reason,
most of the trees that you’re familiar
with on the mainland, you won’t see them on isolated
islands with one exception. And that exception you
are all familiar with. Everyone knows a coconut. But you may not have ever
bothered to think, well, what is a coconut all about? Well, a coconut is a
seed of a palm tree. It’s a seed that’s very well
adapted to floating in water and germinating somewhere else. And so you’ll find palm trees
on islands all around the world because their seeds are
well adapted to dispersing through the ocean. Now let me just give you
an example of one island. Well, the result of
all of these problems is that many islands don’t
have a lot of species compared to the nearest mainland because
so many types of organisms can’t get there. Let me give you one example
of this– the island of Cocos Island. It’s in the Pacific Ocean. It’s owned by Costa Rica. It’s about 300 miles
southwest of Costa Rica. And on Cocos Island,
here is the fauna. There are no amphibians. There are no
terrestrial mammals. There are only two
species of lizards. Now this is extraordinary
because Costa Rica has one of the richest
lizard faunas in the world. Hundreds of species of
lizards occur in Costa Rica, but only two of them have
made it to Cocos Island. Birds– there are
90 species of birds. But again, Costa Rica
has hundreds and hundreds of species of birds. And most of them have
not made it to Cocos. In fact, many of these
90 species are sea birds. Now, I’m an
evolutionary biologist, so of course I’m not
supposed to call them birds. I’m supposed to
call them dinosaurs. But that does remind
me that Cocos Island has been in the news lately. Maybe you’ve heard about it. [VIDEO PLAYBACK] [MUSIC PLAYING] There’s Cocos Island. They’re building
a new theme park. It’s about to open. [ROAR] [SPLASH] [CHEERING] [MUSIC PLAYING] What could possibly go wrong? [LAUGHTER] [END PLAYBACK] Now, the reason I mention this
is, of course, in Jurassic Park and in Jurassic World,
the island is Isla Nublar. But Isla Nublar is Cocos Island. Isla Nublar is supposed to
be a Costa Rican island. Isla Nublar means
“cloud island.” Cocos Island is the only
island in the Eastern Pacific that has a cloud forest. It’s clearly Cocos Island is
what Isla Nublar is based on. So I thought if nothing
else from this talk, you’ll have this
interesting little nugget that you can tell people. The movie opens in
less than two months. Incidentally, the
people of Costa Rica, when Jurassic Park
came out, there were people who were outraged
because Cocos Island is a national park. And the thought that Costa Rica
would allow a biotech company to turn a national park into a
theme park– some people were furious at it. Anyway, a little information
about Cocos Island. Well, what is the significance
of all of these species being absent from islands? Part of the significance
is the species that get there have a
lot of opportunities available to them. The resources that are
used by the species in the mainland that
didn’t get there, those resources are available. So for example, if hummingbirds
don’t make it to the island then the nectar is available
for some other species to take advantage of. And so there are lots
of unused resources because of the depauperate
fauna of these islands. And so that gets us to
our next question– what happens to these species once
they colonize the islands? Well, I want to
digress for a moment to tell you a brief story about
a talk I heard a few years ago. It was by a
historian of science. His name is Peter Bowler. He’s an expert on Darwin,
and he gave a talk asking the question
what if, the sort of question we ask all the time. But his question had to
do with Charles Darwin. Now as you all know, Darwin
circumnavigated the globe on the HMS Beagle. And there he made
many observations that led him to come up
with his idea of evolution. And so Bowler asked
a simple question– what if the Beagle had sunk? What if Charles Darwin had
gone down with the ship and had not lived? Well, of course, that would
mean that his book The Origin of Species would
not have been written. And the question
that Bowler wanted to ask was how would our
understanding of evolution have progressed in the
absence of Charles Darwin? Now as you all know,
Darwin was only one of two people who proposed
the theory of evolution by natural selection. It was proposed simultaneously
by Darwin and Alfred Russel Wallace. Wallace was the great
explorer and scientist who did his research,
among other places, on the islands of the
East Indies– in Malaysia and Indonesia. And he came up with the idea of
evolution by natural selection, as well. And so Bowler went
on about, well, would Wallace have been
able to carry the day? Or if not, when would the
idea have been developed, and so on and so forth? And it was an interesting idea. I’m not going to tell you
what his conclusions were. I’d be happy to talk
about that later. But it really got me
thinking, this idea of what if events had
occurred differently. And so I want to propose my
own scenario– my own “what if” concerning Darwin. It won’t be so dramatic as
him dying on the Beagle. But suppose the Beagle’s
voyage had been a little bit different. How might our understanding
of evolution have changed? Before exploring this
scenario, though, I want to review what it was that
Darwin saw on the Beagle that so impressed him– that so got
him thinking about evolution, particularly in the Galapagos. And there were two things in
particular that Darwin saw. First was the phenomenon
of geographic variation– of species that differ from
one species to the next. And so Darwin was
very impressed when he was informed by the vice
governor of the Galapagos, a Mr. Lawson, who said that
he, Mr. Lawson, if you gave him a tortoise shell, he could tell
you what island it was from. In other words, that there
was variation from one island to the next, and
it was so profound that you could identify
the island just from looking at the shell. And this got Darwin thinking,
well, why should this be? If islands were specially
created by the Creator, why should they vary from
one island to the next? And then he observed the
same thing for himself when he started looking
at the mockingbirds, which he called mocking-thrushes. And he said, “to
my astonishment, I discovered that all of
those from Charles Island belonged to one species,
all from Albemarle Island to a second, and all
from James and Chatham Island to yet a third.” And so this really
got him thinking, maybe species aren’t immutable,
as it was so believed. Maybe they could change. And that certainly planted the
seed of the idea of evolution. The second thing that Darwin
saw had to do with these birds– these finches that
occur in the Galapagos and now bear his name. We now refer to them
as Darwin’s finches. Well, Darwin collected
a bunch of these birds when he was on this trip. But to be honest, he didn’t
pay much attention to them. He didn’t think they were very
significant because he thought they were members of a number
of different families of birds that he was familiar with
from his time in Europe. He thought that the big-beaked
bird was a grosbeak. The little one he
thought was a warbler, and these two he
thought were finches. And see, he thought this
was nothing special– just the local representative
of families that are found throughout the world. Well, when the Beagle
got back to England and Darwin went ashore,
he turned his specimens over to specialists
in different areas. And so he turned
his bird specimens over to John Gould,
probably the most famous, the most noted
ornithologist of the time. Gould studied the
specimens and came back to Darwin several weeks
later and pointed out that Darwin was wrong,
that these birds were not members of different families
that occur in Europe. Rather, they were all
members of a single family– a family of birds hitherto
unknown to science that only occurred
in the Galapagos, which he gave the
name Geospizadae. So these were all members
of a family of birds only from the Galapagos. Well, Darwin immediately
realized the significance of this. And as he wrote in his
bestselling travelogue, Voyage of the Beagle, in 1839, “Seeing
this gradation and diversity of structure in one
small, intimately related group of birds,
one might really fancy that from an original paucity of
birds in this archipelago, one species has been taken and
modified for different ends.” I mean, there you
have it right there. This is evolution. In 1839, Darwin was very clear. He understood evolution, and
he understood the mechanism natural selection. Now it took 20 years for him
to actually publish his book. But it’s very clear
that his observations on the Galapagos and elsewhere
helped him develop these ideas. Well, the question I want to
ask– the “what if” question– has to do with the
instructions that were given to the captain of
the Beagle, Captain Fitzroy. Fitzroy was given these orders. “You are required and
directed to put to sea and to proceed with all
convenient expedition, successively to Madeira or
Teneriffe; the Cape de Verd Islands; Fernando
Noronha”– in other words, going down the west coast
of Europe and Africa, then across to “South
American station to perform the operations
and execute the surveys.” Well, the question
I would like to ask is suppose that they had not
been sent on their expedition, but they had been
sent elsewhere? Specifically, suppose
the instructions had been to go to Cuba,
Hispaniola, Jamaica, and Puerto Rico– in other words, not
circumnavigating the globe but to the Caribbean islands? What would Darwin
have seen there, and what would he
have thought of it? Well, I’ll tell you what
he would have seen there because this is where I’ve
spent my entire career doing my research. He would have seen lizards,
particularly the lizards that I study. And I hope you’ll
humor me by letting me talk about my lizards
for a little bit, lizards in the genus Anolis,
incredibly abundant lizards that are all over the place
and incredibly species rich. 150 or more species occur
on Caribbean islands. Well, Darwin was a great
naturalist– a great observer. He would’ve noted these lizards. He would have studied
their differences. And I think he would’ve come to
very much the same conclusions that he did by going
to the Galapagos. Now I should point
out for starters, Darwin was aware of lizards. He certainly saw some fantastic
lizards in the Galapagos. For example, the marine
iguana– one of the most amazing lizards around today. This is the only ocean-going
lizard in the whole world. It goes swimming in the ocean. It eats seaweed– algae. It goes underwater,
dive down to the bottom, and munches on
seaweed underwater. Then it comes up and it
blows– you’ve probably seen pictures of them blowing
salt out of their nostrils because they get
all the seawater, and they get rid of the salt by
blowing out of their nostrils. Just an extraordinary animal. And undoubtedly, we would
think that Darwin would be very impressed by the marine iguana. Well, here’s what he had to say. “It is a
hideous-looking creature of a dirty black color, stupid
and sluggish in its movements.” All right. So Darwin wasn’t so impressed
with the marine iguana. But the marine
iguana has a cousin. And this is a beautiful
animal– the land iguana. Golden yellow in color, it
plods around– 5 feet long. It eats cactus. Darwin surely was
impressed by this species. Well, maybe not so much. “They are ugly animals. From their low facial angle,
they have a singularly stupid appearance.” All right. So he wasn’t impressed by
the iguanas of the Galapagos. Nonetheless, I would
contend that he would have been
impressed by lizards like this, Allison’s anole,
a beautiful animal from Cuba. Well, what would
Darwin have seen? He could not have missed seeing
this because these lizards are so abundant. What he would have found
was that on each island, the species of anolis
lizards are very diverse. They live in different
habitats, and they have different
anatomical features that are adaptations to the
part of the habitat they occupy. And strikingly, if you go
from one island to the next, you see the same set of habitat
specialists on each island. And so I want to
briefly show you what these lizards are like. The first species we call
the trunk-ground species. It lives on tree trunks. And it runs down
to the ground where it fights with its fellows,
and it catches prey, and so on. These are lizards that
have long hind limbs that let them run fast and jump far. They’re very muscular. They have very small
little toe pads, and they’re brown in color. These are the trunk-ground
species of several islands. And this structure is called
dewlap or a throat fan. The males stick them out to
communicate with each other. Then there’s the
trunk-crown species. These are species found on the
trunk up high into the tree. They get out into
the vegetation. And to do that,
they particularly have large toe pads
that let them stick on to smooth surfaces. We actually have one of these
up in the exhibit upstairs. And this afternoon,
it was sticking to the glass with its toe pads. And you should go take
a look at them there. They’re also green in color. Here are the trunk-crown
species of several islands. Next are the crown-giants. These are also high
up in the tree. But these are the
largest anoles. They’re maybe about this big. And so they’re on
big vegetation. They are large lizards– a
big head, a vertebral crest. They can also turn color
from green to brown. These are also the most
aggressive of the anoles. They will stand and
defend themselves. And in fact, I’ve found
this out the hard way. It’s very dangerous work
working with these lizards. Don’t try this at home. Here are the crown-giants. Next are the grass-bush lizards. These are the smaller
ones that live in the low-lying vegetation. They’re on ferns or
even on grass blades. They’re slender. They have short
forelimbs, a long head, an extremely long tail– as
much as four times the length of their body. Here are some of the
grass-bush anoles. And finally, the most
unique are the twig anoles. These are the species that
use the very narrow twigs. And they move very slowly. So they have very short limbs
to keep them from toppling off these narrow twigs. They have a long head. They’re also very light
in color– camouflaged– because they can’t run away. Their legs are too short. They’re not very fast, so they
have to rely on not being seen. And here are the twig anoles
of the different islands. Well, Darwin wouldn’t
have known this. But it turns out one interesting
fact about these lizards is that these similar
types on different islands are not closely related. They have independently
evolved to be very similar. So these four twig anoles
on the different islands have independently
evolved to be twig anoles. We can see this when we look
at a evolutionary tree, what we call a phylogeny. This shows the
evolutionary relationships. Each one of these little
tips is a species. This is for the trunk-crown
anoles and the different colors on the different islands. And you can see the trunk-crown
anoles on the different islands are not closely related. They would be all in
one clump if they were. And so they have
independently evolved to be trunk-crown anoles. And this is true of all
the other types, as well. And so even though each
island has six different types of habitat specialists–
the same six types– they have evolved independently
on each of the islands. Well, what would Darwin
have made of all of this? He certainly
would’ve noticed it. These are very common
lizards– very easy to find. If you’ve ever been
to the Caribbean, you undoubtedly have seen them. Well, he was impressed at the
variation of mockingbirds– that there was one species on
one island, a different species on another. He would’ve been
equally impressed by, say, the twig
anoles– that there was one species of twig
anole on one island, another species on
another island– the same sort of variation. And just as Darwin was impressed
with the Darwin’s finches, he would’ve been impressed
by the different adaptations of the different lizards,
how they had all been derived from one ancestral species. So I would contend
that if Darwin had gone to the Caribbean
instead of the Galapagos, he would’ve had
the same thoughts. He would’ve had the same
ideas leading to his thoughts about evolution. But why stop at the Caribbean? Let’s continue a little further. Suppose instead of
going to the Galapagos at the end of his trip,
he’d gone up to Hawaii– the most isolated island
group in the world. What would he have
seen in Hawaii? He would’ve seen these
incredible birds called honeycreepers–
all the descendants of a single species of finch–
with this amazing diversity of beaks. They have these very
long curved beaks for sipping nectar, big
peaks for crushing seeds or eating fruits, little beaks
for picking out insects– a huge variety of
different beaks for species living and using
different food sources. Well, if Darwin was impressed by
this variation in the Darwin’s finches, which is quite
large, imagine what he would’ve said about this. It would’ve blown his mind. I think if he’d
been to Hawaii, he would’ve published the
Origin of Species right away. Now, in Hawaii, Darwin would
have seen other things, as well, such as
the silverswords– these plants–
again, all descended from one ancestral type that are
as varied as a bush like this, an agave-like plant
like this that has these big inflorescences,
and some trees– all of these descendants
of one species. Or finally, let’s try
one other “what if.” What if at the end
of the trip, when they sailed across
the Indian Ocean, if instead of sailing
just by Madagascar they had actually stopped
and visited Madagascar? What would Darwin
have seen there? Well, we actually have
some idea because recently some other explorers
visited Madagascar, and we can look
at what they saw. I refer, of course,
to these guys. And here’s what they saw. [VIDEO PLAYBACK] -(SINGING) I like
to move it, move it. I like to move it, move it. You like to– -Move it. -I like to move it, move it. I like to move it, move it. I like to move it, move it. You like to– -Move– [END PLAYBACK] [LAUGHTER] Lemurs– they would’ve seen an
incredible diversity of lemurs. And I have to say
that DreamWorks did a pretty good job–
at least I think so– of portraying the diversity
of lemurs on Madagascar. You’ve got your aye-aye, your
mouse lemur, your black sifaka, ruffed lemur, and so on. They did make one
mistake, however, and that is King Julian,
the ring-tailed lemur. The mistake is that
the ring-tailed lemur is one of those few species of
primates in which the female is the dominant animal. And so King Julian
should’ve been Queen Julia. This was actually pointed out to
Jeff Katzenberg, the director, or producer, or whatever
before the movie came out, and he didn’t want
to hear about it. Well, here’s maybe a little
bit more accurate view of the diversity of
lemurs around today. But it turns out
that this is just a shadow of the total
diversity of lemurs because in fact other
lemur species evolved that are no longer present. Now Darwin, you may
not realize, not only was he a great
biologist, but he was also a pretty good paleontologist. And when he was
in South America, he made a number of
important fossil discoveries. And I think in Madagascar, he
would’ve done the same thing and found evidence of some of
these extinct lemurs– lemurs that were sadly wiped out
by the first people who got to Madagascar in the
last millennium or two. For example, there was this
animal, palaeopithecus, an animal that hung upside
down like a tree sloth. It had long arms with
curved arms and digits to hang in a suspensory mode. Except tree sloths
are a few pounds. This animal was 75
pounds in weight. Or megaladapis, an
animal whose proportions were very similar to a koala. And we’re not quite sure
exactly how it lived. But it probably hugged
trees like koalas did, except that this
animal was 100 pounds. But the biggest lemur was
a terrestrial species, archaeoindris. This animal was the
size of a gorilla. So all of these animals were
part of the lemur diversity. As I said, they went extinct. They were wiped out by humans
in the last few centuries. There are other things that
Darwin would have seen, as well as the
diversity of lemurs– these birds called vangas,
which have a diversity of bill shapes comparable to
honeycreepers in Hawaii. However, if Darwin had taken
these specimens to John Gould, Gould would not have
been able to set him straight because even until
very recently, ornithologists thought that these birds were
members of different families. It was only when scientists
sequenced their DNA that we realized that it’s
all one family of birds– the descendants of a
single ancestral species that got to Madagascar
and proliferated. In fact, there are all kinds
of groups in Madagascar. I haven’t talked about the
chameleons or the tenrecs. And you’re going to have to
go to the exhibit upstairs to see something
about them, as well. So my bottom-line point here
is that it really almost didn’t matter where Darwin went. Almost any major island
has had this phenomenon of a species
diversifying wildly, just like the
Darwin’s finches did. It’s a phenomenon that
we have an name for it. It’s called adaptive radiation. And it refers to
the diversification that occurs when an ancestral
species reaches a place and then diversifies to occupy
many different ecological niches. Well, it turns out that adaptive
radiation is a phenomenon most clearly seen on islands. In fact, if you have a
textbook and you look up adaptive radiation,
you’ll probably see one of the
examples I’ve given you or some other one from islands. It’s something that happens
very clearly and most often on islands. Now why is that? Well, I’ve already
told you the reason. It’s because of the
ecological opportunity. Because so many species
don’t get to islands that there are
resources available that wouldn’t be
available on the mainland. A finch on the mainland
can’t start sipping nectar because there are
already species that are specialized to do that. But you take it out
to an island where there’s no humming
bird or anything else, those resources are there. And they can start
adapting to that resource. And so the opportunity
that is afforded by the lack of
colonizationability of so many species is what
prompts adaptive radiation. Well, adaptive radiation
is a predictable result of what happens on islands. But in general, how predictable
is evolution on islands? This is my last question. It turns out there are two
schools of thought about this. On the one hand,
there are some people who argue that evolution
is very predictable. For example, George McGhee,
a theoretical biologist at Rutgers University,
suggests that if we find life on another
planet, that life there will look strangely familiar–
that the outcome will be very similar to evolution on Earth. This idea has been taken
even further by Simon Conway Morris at the other Cambridge–
the University of Cambridge in England. He argues that the demands
placed on organisms by the environment are very
strong– in other words, the aerodynamics of how to
fly or how to crush a nut or how to dig– and that
there are optimal solutions to these problems. And so natural
selection leads species to evolve the same sort of
adaptations time and time again. And so he argues “the
constraints of life make the emergence of the
various biological properties very probable, if
not inevitable.” He goes so far as to say, making
“the emergence of something like ourselves a
near-inevitability.” So what McGhee and
Conway Morris are arguing is that
evolution doesn’t have a lot of different
solutions, that you face a species with
a particular problem, it will evolve in
a predictable way. This view, however,
is not unanimous. And probably the biggest
opponent of this view was our very own Stephen Jay
Gould– the late Stephen Jay Gould– one of the greatest
evolutionary biologists of the last century. And Gould took the
exact opposite tack. He argued that evolution
was not at all predictable, that it was very
haphazard and contingent, that the events that
occur in history could send evolution
in one way or another. One extreme example had to
do with the asteroid that wiped out the dinosaurs at the
end of the Cretaceous period. Imagine that that asteroid
hadn’t actually hit Earth but had just mixed– that its
path had been a little bit different. Well, if it had missed
Earth, the dinosaurs would still be here. And where would we be? We’d still be in little
bushes acting like an opossum. Well, that’s an extreme example. But Gould argued that
even little events could send evolution in
different directions. “Any replay” of the history
of life– in other words, we start it again–
but you altered it by a little bit– an
“insignificant jot or tittle at the outset would’ve
yielded an outcome of entirely different form.” So Gould’s argument
is that evolution looked very idiosyncratic,
that events could send it in different directions. Well, the problem
with this debate is it’s really impossible to get
evidence one way or the other. We can’t get 10 Galapagos
Islands and seed them with a finch and see if the same
outcome occurs time and time again. We can’t hit some planets with
an asteroid and not others. Maybe someday we will find
life on other planets, and we can test that idea. But until then, it’s
a very difficult idea. But this is where the idea of
islands as test tubes come in. We can look at what has
occurred on different islands and see how similar the outcome
is from one island to the next. If evolution is
indeed predictable, as Simon Conway Morris
and McGhee argue, then we would expect
very similar outcomes on different islands. On the other hand, if
it is idiosyncratic, as Gould suggests, then we
expect to see a lot of things evolve on only one island
with no parallels elsewhere. Well, what do the data suggest? There are some examples
of repeated occurrences. The anolis lizards that I
talked about are probably one of that best examples,
where the same set of habitat specialists have
evolved independently on four different islands–
a very predictable, deterministic outcome. There aren’t very many other
examples like that, though. There are some snails
on islands near Japan where three types of
habitat specialists have evolved multiple times. But those are really almost the
only two really good examples. Then there are less
stringent examples. In Australia– if we want
to consider Australia an island– people like to line
up the Australian marsupials and point out that they
have parallels elsewhere in the world. But this isn’t saying
that two places have evolved the same faunas. They’ve just shown that
Australia has a lot of matches in many different places. So it’s not like
the two have had the exact same
evolutionary outcome. And moreover, although
there are a lot of matches for
Australian animals, there are a lot of things
that there are no matches. There’s no kangaroo or koala
anywhere else in the world. So really, the evidence
for repeatability on different islands, at least
in my view, is not very strong. What about the
opposite– Gould’s argument that evolution
is idiosyncratic? I would suggest that there are
lots of examples of evolution doing what I call a
one-off– a species that evolved on one island and
there’s nothing like it anywhere else. And let’s start off with the
greatest animal of all time, the duck-billed platypus. Here’s an animal that
lives– paddles around in creeks in Australia eating
crayfish and other things. Nothing like it has evolved
anywhere else in the world. If evolution was
repeatable, we ought to have platypuses at least in
the Southeastern United States. I want my platypus. But it’s not here. It’s a one-off
only in Australia. Here are a few other
examples– the giant earwig of St. Helena, an enormous bug. If you remember the
Star Trek movie where they put the bug in Chekov’s
ear, that’s what this was, I think. The solenodon of
Hispaniola, an animal that goes snuffling around
in the leaf litter trying to find insects. It looks like something
out of Dr. Seuss– nothing like it anywhere
else in the world. The tree lobster of Lord Howe
Island– actually a big walking stick. It’s now limited to this crazy
island called Ball’s Pyramid. A caterpillar in
Hawaii– now, we all think of caterpillars as these
lovable, peaceful creatures. We learn about them
in grade school. They go along munching
leaves and so on. Well, think again. [VIDEO PLAYBACK] [MUSIC PLAYING] -This is a carnivorous
caterpillar. The carnivorous
caterpillars of Hawaii. [END PLAYBACK] Or my last example from Cuba– a
3-foot-tall owl– 3 feet tall– and it doesn’t fly. So you could go on and on, this
list of idiosyncratic things that have evolved on one
island– no parallel anywhere else in the world. Or we could test this idea of
repeatability in another way. We can look at species that
use the same resources– the same ecological
niche, if you will– and ask if they’ve evolved to
use that niche in the same way. And so if evolution
is repeatable, you’d expect them to
evolve the same adaptation. Simon Conway Morris
would say, they’ll evolve the best way of doing it. Gould would say, they’ll
find different ways on different islands. Let’s talk about a bird
we all know– woodpeckers. Now if you ever
really thought, here’s how a woodpecker finds its prey. It’s got this really stout beak. And it pecks around
on a tree trying to find a hollow
space by the echo. When it finds a hollow space,
it goes pound, pound, pound, pound, pound– 20 times
a second– hitting it with its peak,
which is reinforced. And its brain has
reinforcing to keep it from getting a concussion. And people are studying
how they do that. So it digs a hole to get
at the grub or the larvae. And then once it gets the hole,
it sticks its long tongue in to snare the grub. And their tongue actually
wraps around the brain. And that’s how they have
room for such a long tongue. And so that’s how
they get their prey. Well, it turns out
that woodpeckers don’t colonize very well. You don’t see them on
most isolated islands. For some reason, they just
don’t do very well at that. And so on many
islands, other species have moved into that niche
of eating larvae like grubs and larvae and so on. On Hawaii, it’s a species called
the akiapola’au– something like that. And if you look at
their beak, they’re not the same as woodpeckers. And in fact, their beaks– their
upper bill and their lower bill are very different. Their lower bill is very stout,
somewhat like a woodpecker’s. And they don’t bang
it away, but they chisels a hole in the wood. And then once they
have the hole, they use their curved upper beak
to reach in and snag a prey. And so that’s how
they get larvae. Now in New Zealand, there’s
a bird, sadly extinct, called the huia, in which those
two bill functions have been split into the different sexes. The male has the stout
bill where it digs a hole by chiseling away at the wood. The female has a curved beak
that reaches in the holes to extract the prey. Now it used to be thought
that they worked as a team– that the male did the hole and
that the female reached in. That was a great
story, but it turns out we don’t know if
that’s true or not. Unfortunately, we don’t
know much about them because they’re extinct. And we just don’t know. Maybe they did that. Maybe they had just different
ways of getting prey in inaccessible areas. So those are two alternatives
to woodpeckers to digging a hole and getting the prey. There’s a third species that
does this– one of the Darwin’s finches, the woodpecker finch. It has a rather
unexceptional beak. But it’s found a different way
to extract prey from holes. [VIDEO PLAYBACK] It uses a tool. Here it’s [? stashing ?]
its implement. -Yes, just right. And that’s how it
makes its living. [END PLAYBACK] Pretty remarkable. But even remarkable
is the last example I’m going to show you– the
last woodpecker-type animal. But it’s not a bird at all. It’s a type of lemur in
Madagascar called the aye-aye. And the aye-aye has
a remarkable way of extracting grubs from holes. [VIDEO PLAYBACK] [MUSIC PLAYING] -To find its prey, it
uses a multipurpose digit. [TAPPING] The changes in sound build a
mental map of hollow channels inside. It cups its ears to
gather the slightest vibration that could signify
something to eat, like a grub. Sharp incisors
rip away the bark. Its bony middle
finger changes roles from a scanner to a scraper. The aye-aye locks in. The finger transforms
into a hook. A sharp fingernail
impales the grub. It’s dragged up, out, and
into the aye-aye’s mouth. [END PLAYBACK] Yummy. [LAUGHTER] Well, I think this is strong
evidence for Gould’s argument– very different ways of
solving the same problem. Evolution is not
at all predictable. It goes about it
in different ways. But I want to take this point
one step further and think about entire alternative worlds. And in particular,
let’s get back to that asteroid that
wiped out the dinosaurs. What if it had wiped out
the mammals, as well? What would’ve happened? How would life have evolved
in the absence not only of dinosaurs but mammals? Well really, there’s no way
of answering that question. Or maybe there is
because there’s one place in the
world where there are no terrestrial
mammals at all– one very interesting place. I refer to New
Zealand, these islands 1,000 miles off the
coast of Australia. And for whatever reason,
are no mammals on Australia. Let’s take a look at
what has evolved there. Let’s start with the
remarkable bird the kiwi. Some people refer to it
as an honorary mammal. Look right here, for example. It’s got whiskers just like
a cat, right on its forehead. Let’s look at some other ways
that the kiwi is like a mammal. [VIDEO PLAYBACK] -Is an evolutionary oddity. [MUSIC PLAYING] For a start, it’s
an honorary mammal. Told you so. -Unlike any other
bird, his nostrils are situated at the
end of his beak, allowing him to detect prey
up to 6 inches underground. And his weird plumage
is more like shaggy dog fur than feathers. The youngster is intruding
on another kiwi’s territory. [SHRILL BIRD CRIES] That’s where they get
their name– kiwi, kiwi. -And knowing he’s been
detected, he takes off. The chase reveals all
kiwis’ most startling evolutionary feature. Instead of flying, they run. [BIRD CRIES] [END PLAYBACK] So the kiwi is sort
of mammal-like. But most of the other
denizens of New Zealand are not particularly
like mammals. For example, the major
herbivores of New Zealand were not anything like
deer or antelopes. They were these large relatives
of the kiwi, the moas, the largest of which got
to be almost 10 feet tall. And these were the herbivores. There were 11 different
species of them. Unfortunately, they
are all extinct now, hunted out by the
early New Zealanders. In addition to the moas, the
world’s largest bird of prey, Haast’s eagle, preyed
on some of these moas. Then there is the kakapo,
a flightless parrot. I mean, think about this–
a parrot that doesn’t fly. It just walks around on the
ground eating fruits and foods like that. And there are not many
predators in New Zealand. And so another parrot
has become carnivorous. This is a bird, the
kea, that is reputed to attack sheep, not to kill
them but to peck at their backs and eat little chunks of them. They also have become adept at
destroying windshield wipers. [LAUGHTER] There’s the huia I talked
about– the woodpecker replacement. And so there are
all these birds that have evolved in very
interesting ways. But it’s not just the birds that
have done interesting things. For example, there
are giant flightless crickets called
wetas shown here– a younger version of myself. There’s a hamburger-sized
giant land snail. And then there are these bizarre
plants– they have a trick. They’re called divaricating,
and what they’ve done is that they have the
branches on the outside and the leaves on the inside. It’s backwards. A number of
different plants have evolved this in New
Zealand, presumably an adaptation, a defense
against moa herbivory. So there are all these
different unusual adaptations of New Zealand animals. But perhaps the
most unusual one has to do with one of
the few mammals that is there– one of the bats, the
New Zealand short-tailed bat. Now, the famous
biologist Jared Diamond referred to this bat as
the bat’s family attempt to make a mouse. As we’ll see,
however, he probably picked the wrong mammal
to compare it to. [VIDEO PLAYBACK] -They can fly all right. But our infrared camera
reveals that they also have a very unbat-like
way of hunting. They land on the ground and
forage through the leaf litter just like shrews. [RUSTLING AND SQUEAKING] Terrestrial bats. -They’re walking
on their wrists, with the bones of their
fingers pointing upwards and slotted into a groove
along the upper arm. [SQUEAKING] Now they seem to be
hunting as a pack. Insects or other small creatures
in the leaf litter fleeing from the jaws of one run
straight into those of another. [SQUEAKING AND RUSTLING] [MUSIC PLAYING] Worms are a great favorite–
so much more satisfying than several hundred mosquitoes. And they don’t want to share
them with one another, either. They complete their
meal with a drink of nectar from the Hades plant
that bloom flat on the ground. They’re this
plant’s pollinators. Relationships between a
plant and its pollinator– [END PLAYBACK] So what New Zealand shows is
that a world without mammals– or without many mammals– would
be very different from the one that we’re used to
everywhere else– I think very clear
evidence of the lack of predictability of evolution. To me, islands very clearly
show that island evolution is idiosyncratic. Now does that mean that
there is no predictability to island evolution? No. There are some
consistent generalities that do characterize
what happens on islands, and I’m going to end my
talk with just a couple more minutes telling you about
what some of these generalities are. Probably the most famous one
has the very uninformative name of the Island Rule. And it has to do with
size evolution of mammals on islands. And what happens is
that big animals tend to get smaller– big mammals
on islands– and little ones– up to, say, the size
of a fox– get bigger. Now the most famous
example of this– it’s much more dramatic, the
ones that get smaller. And the most famous
example has to do with elephants on islands. This is a species
of elephant that used to be found in
the Mediterranean. It was around in
the Pleistocene, relatively recently. Now take a close look here. This is my friend Louise Roth,
a professor at Duke University. And she’s kneeling. And even though
she’s kneeling, she’s still taller than
this male elephant. And take a look. This is a baby elephant. These were tiny
little elephants. And these tiny elephants
evolved on a number of different islands. In addition to dwarf
elephants, there were also, oxymoronically,
dwarf mammoths that evolved on a number
of different places. For example, one
of these places, Wrangel Island here in
Siberia– these dwarf mammoths were around until
about 4,000 years ago. So think about that. While the pyramids
were being built, there were dwarf mammoths
still in Siberia. So these puny pachyderms,
as I call them, occurred on islands in
many different places around the world. Now some of you may
be aware that there’s been a lot of discussion lately
about maybe we could somehow recreate a mammoth. There are all these
frozen carcasses in the permafrost in Siberia. And perhaps we could
recreate the mammoth. My friend, my
colleague Beth Shapiro, has just written
a book– it’s just out– How to Clone a Mammoth. And it’s really
a brilliant book. I highly recommend it. But I think Beth didn’t
quite get it right. We don’t want to really
recreate a mammoth. We want to recreate
a dwarf mammoth. Think about how
great that would be. [LAUGHTER] What a great companion. But these dwarf mammoths
would be more than just pets. They could also be
service animals. And this was actually
realized years ago in the town of Bedrock. [LAUGHTER] Now, for what it’s worth, while
I was preparing this talk, I came across this picture. This is a dwarf elephant on
the island of Sri Lanka that was recently reported. If you look at this
elephant, it’s an adult male. But its proportions
are a little bit funny. And in fact, here’s
the same elephant right next to a
normal-sized elephant. And so I’m not saying
that dwarf elephants are evolving in Sri Lanka. But you can see how this
process might get started. A mutant animal
that’s somehow favored could begin the process
of size reduction. Island dwarfism has occurred
in many animals on islands. There are very small hippos
that evolved in Mediterranean islands and elsewhere. There were small deer
on Jersey Island. The fossil record
shows them reducing by 80% over a period of
a few thousand years. On the island of Flores,
there was not only a dwarf elephant–
only 3 or 4 feet tall– but recent fossil evidence
you probably heard about, the famous Hobbit, a hominid
species this tall– homo floresiensis– that was
around until 20,000 years ago. 20,000 years ago, there
was another species of hominid existing
in the world. And it was this dwarf
species occurring on an island in Indonesia. We actually have a cast of the
skeleton up in the exhibit. And take a look at this
really remarkable– this remarkable person?–
another species of hominid, a dwarf one, from islands. So why this dwarfing
occurs is much debated. It may have to do with a lack of
resources– combination of lack of resources and
lack of predators. Many animals are big,
in part to defend themselves– to make themselves
invulnerable to predators. In the absence of predators,
they don’t need to be big. And also, their populations get
very large because they’re not contained by predators. And they eat up the resources,
and so smaller animals need less food. Those may have been
the selective pressures that favor dwarfism. Now as I said, this rule
applies only to mammals. It’s not clear that it applies
to other types of animals. Maybe it does. Maybe it doesn’t. But it’s certainly the case
that other types of animals, there are examples of big
things getting even bigger. So for example, in birds,
the largest bird ever to live– the elephant
bird in Madagascar– this was a bird 10 feet tall
that weighed half a ton. The largest egg of
anything ever known– we have a cast of one upstairs–
occurred in Madagascar as recently as 500 years ago. Of course the Komodo dragon,
the largest lizard in the world today on the small
Indonesian island of Komodo. So that’s one predictable
pattern– size evolution on island. Now I want to quickly run
through a couple of others. Many animals lose their
ability to fly on islands. Many birds have become
flightless, such as the kiwi, the dodo of Mauritius. Many insects– many types
of beetles and moths and other animals become
flightless on islands. Why they do that,
it’s not clear. It may be, again, due
to lack of predators. So they don’t need
to fly around. So why bother investing the
energy in producing wings? Many island animals
become tame, again, probably because there
aren’t many predators. The animals in the Galapagos
are famous for their lack of fear of people. And this is true of many
other island animals. Of course, this was the
downfall of the dodo. When they were discovered
on the island of Mauritius, sailors would just come up
and club them over the head. And alas, they clubbed
them into extinction. The last example I’m going
to talk about are trees. I mentioned earlier that
trees don’t get out to islands very well because
their seeds don’t disperse across sea water. Well, what happens is plants
do get out to islands. And then there are no
trees shading them. And so it’s an advantage to any
sort of little shrub or weed to get a little bit taller to
get taller than your neighbors and get all of the sun. And so there are species of
plants that on the mainland are all these little
bushes and shrubs. But on islands, they
turn into trees. For example, in Saint
Helena, the cabbage tree is a type of plant
that normally produces cabbages or those
sorts of little plants. But on Saint Helena,
it’s become a tree. In the Galapagos, there are
forests of scalesia plants, a relative of the sunflower. But on the Galapagos,
they’ve evolved into a number of different species of trees. Also on the Galapagos,
cactus have become trees, and so again, it’s an example
of ecological opportunity. The lack of trees, other species
take over and turn into trees. It’s a very common phenomenon. Well, finally I want to
make one last prediction about the predictability
of evolution. And my prediction is
that you are going to love the exhibit upstairs. There’s all kinds
of great stuff. And so I’ve talked
long enough already. I’m going to end my
talk by thanking you for your attention. I’ll take a few
questions, and then we should all go upstairs and
look at this great exhibit. [APPLAUSE] So thank you very much.

Reader Comments

  1. This talk was very thought provoking and entertaining! I send my gratitude towards Dr. Losos and to Harvard Museum of Natural History for uploading this fascinating lecture.

    P.S. If you could upload a video whenever you have a lecture on animal behavior similar to Dr. Hoekstra's lecture, that would be very much appreciated.

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