How Do Unrelated Species Develop Similar Traits?

Some traits and abilities -- like flight, for example -- are so useful that completely different species evolved them independently over time. Learn about convergent evolution (and divergent evolution) in this episode of BrainStuff.

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Episode Transcript

Speaker 1 (00:01):
Welcome to Brainstuff production of iHeart Radio. Hey brain Stuff,
Lauren bobble bomb here. You may have noticed that although dragonflies, bats,
and say California condors all have the ability to fly,
they aren't very similar in any other way. It's not
very likely that any of these animals had a common

(00:23):
ancestor any time in the past six million years or so,
and definitely not one particular shared ancestor that first figured
out how to haul its body off the ground and
zoom around in the air. And yet they all developed
the ability to fly separately. This is an example of
what scientists call convergent evolution. Evolution doesn't do things on purpose.

(00:47):
It's not sitting at a big desk in a corner
office somewhere making decisions about which animals lay eggs or
get pouches on their tummies. Evolution is the process of
organisms changing over the course of many generation sans to
suit the conditions under which they live, and some traits
like flying, are particularly useful. It can help you catch

(01:08):
prey or avoid predators, or easily moved to new food
sources and ecological niches. So it's evolved separately in different
groups of animals. Several times. However, flying doesn't look the
same across the groups. For instance, bats developed a membrane
between their abdomen, arms and fingers to catch air, while

(01:29):
birds sprouted feathers along a finger fused fore limb, which
means bats can maneuver their wings separately, while birds have
to move together. Flying insects just fashioned wings out of
their exo skeletons. So convergent evolution can tell us a
lot about what kinds of adaptions work to help species

(01:49):
survive all the trials and tribulations they might face in
a particular type of environment, but what ecologists call a biome.
For instance, in North America, the kangaroo rat lives in
the Sonoran Desert, where it spends the scorching days in
a cool, dry burrow and the cool desert nights collecting seeds, vegetation,
and the occasional insect if they can get it. Everybody

(02:13):
in the desert wants to eat them coyotes, bobcats, rattlesnakes, owls,
But the kangaroo rat is fast and agile, with powerful
back legs and extremely sensitive hearing, all of which helps
it survive a hard scrabble bottom of the food chain.
Desert biome lifestyle, and although the kangaroo rat doesn't have

(02:34):
an enviable life, it is effective to other rodents on Earth.
The Australian hopping mouse in the Australian Outback and a
species called the jerboah in the deserts of North Africa,
Asia and the Middle East evolved separately and yet incredibly similarly.
But how does convergent evolution happen? This is a trickier question,

(02:57):
and the development of genetic tools over the past twenty
years has been helpful in picking it apart. In a
twenty nineteen study published in the journal Science, a group
of researchers at Harvard University looked at the development of
flightlessness and birds, a trait that's evolved several times over,
and exactly how evolution pulled it off in penguins in

(03:17):
the same way that it did in ostriches. Flightless birds
or rattites can't fly for a couple of reasons. Somewhere
along their lineage, they have lost their keel, the bone
that runs perpendicular to the breastbone on flying birds that
the pictorial muscles attached to, and they have reduced four
limbs arranging from nearly absent in the Kiwi bird, to

(03:41):
still obvious but reduced in size in the ostrich However,
there are many ways the particular convergent traits can evolve.
We spoke with Tim Sackton, director of bionformatics at Harvard.
He said, before genomics, one could use developmental tools to
figure out if the same or different developmental mechanisms seemed

(04:03):
to be involved in convergent phenotypes. But the idea of
levels of convergence same mutation, same gene or same pathway
has developed in large part because it's possible to look
in the genome for these things now. In the rabbites,
for example, we were able to show that the same
regions of the genome the control where and when certain

(04:24):
genes are expressed, are repeatedly evolving in flightless birds. But
this doesn't seem to involve the same nucleotide mutations. And yes,
where some traits converge from completely different corners of the
living world, the opposite is also true. Divergent evolution is
the process by which groups from one species or organism

(04:47):
begin to develop different traits, thereby splitting in two separate species.
This often happens when populations of a species are separated geographically,
and over time they adapt to the conditions of their
new spot, whether it's increased predation pressures or a change
in climate. One famous example of divergent evolution was found

(05:08):
by Charles Darwin and has travels to the Galapagos Islands
in eight thirty six. Darwin's finches, as they're now known,
were a group of tanagers, which are not true finches,
that lived on different islands in the archipelago, the main
difference between them being the shape of their beaks, which
changed over the generations due to the particular foods available

(05:28):
to the birds on the different islands. And one more
example fingerprints. Most non human animals don't have them, except
for close human relatives such as chimps and gorillas, but
koalas have fingerprints to The fascinating thing about human and
koala prints is that, even though they're almost identical, they

(05:51):
seem to have evolved independently. Today's episode was written by
Jescelin Shields and produced by Tyler Clang. For more on
this and lots of other converging and diverging topics, visit
how stuff works dot com. Brain Stuff is a production
of iHeart Radio or more podcasts in my heart Radio,

(06:11):
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