Speaker 1: Welcome to Brainstuff production of iHeart Radio. Hey brain Stuff,
Speaker 1: Lauren bobble bomb here. You may have noticed that although dragonflies, bats,
Speaker 1: and say California condors all have the ability to fly,
Speaker 1: they aren't very similar in any other way. It's not
Speaker 1: very likely that any of these animals had a common
Speaker 1: ancestor any time in the past six million years or so,
Speaker 1: and definitely not one particular shared ancestor that first figured
Speaker 1: out how to haul its body off the ground and
Speaker 1: zoom around in the air. And yet they all developed
Speaker 1: the ability to fly separately. This is an example of
Speaker 1: what scientists call convergent evolution. Evolution doesn't do things on purpose.
Speaker 1: It's not sitting at a big desk in a corner
Speaker 1: office somewhere making decisions about which animals lay eggs or
Speaker 1: get pouches on their tummies. Evolution is the process of
Speaker 1: organisms changing over the course of many generation sans to
Speaker 1: suit the conditions under which they live, and some traits
Speaker 1: like flying, are particularly useful. It can help you catch
Speaker 1: prey or avoid predators, or easily moved to new food
Speaker 1: sources and ecological niches. So it's evolved separately in different
Speaker 1: groups of animals. Several times. However, flying doesn't look the
Speaker 1: same across the groups. For instance, bats developed a membrane
Speaker 1: between their abdomen, arms and fingers to catch air, while
Speaker 1: birds sprouted feathers along a finger fused fore limb, which
Speaker 1: means bats can maneuver their wings separately, while birds have
Speaker 1: to move together. Flying insects just fashioned wings out of
Speaker 1: their exo skeletons. So convergent evolution can tell us a
Speaker 1: lot about what kinds of adaptions work to help species
Speaker 1: survive all the trials and tribulations they might face in
Speaker 1: a particular type of environment, but what ecologists call a biome.
Speaker 1: For instance, in North America, the kangaroo rat lives in
Speaker 1: the Sonoran Desert, where it spends the scorching days in
Speaker 1: a cool, dry burrow and the cool desert nights collecting seeds, vegetation,
Speaker 1: and the occasional insect if they can get it. Everybody
Speaker 1: in the desert wants to eat them coyotes, bobcats, rattlesnakes, owls,
Speaker 1: But the kangaroo rat is fast and agile, with powerful
Speaker 1: back legs and extremely sensitive hearing, all of which helps
Speaker 1: it survive a hard scrabble bottom of the food chain.
Speaker 1: Desert biome lifestyle, and although the kangaroo rat doesn't have
Speaker 1: an enviable life, it is effective to other rodents on Earth.
Speaker 1: The Australian hopping mouse in the Australian Outback and a
Speaker 1: species called the jerboah in the deserts of North Africa,
Speaker 1: Asia and the Middle East evolved separately and yet incredibly similarly.
Speaker 1: But how does convergent evolution happen? This is a trickier question,
Speaker 1: and the development of genetic tools over the past twenty
Speaker 1: years has been helpful in picking it apart. In a
Speaker 1: twenty nineteen study published in the journal Science, a group
Speaker 1: of researchers at Harvard University looked at the development of
Speaker 1: flightlessness and birds, a trait that's evolved several times over,
Speaker 1: and exactly how evolution pulled it off in penguins in
Speaker 1: the same way that it did in ostriches. Flightless birds
Speaker 1: or rattites can't fly for a couple of reasons. Somewhere
Speaker 1: along their lineage, they have lost their keel, the bone
Speaker 1: that runs perpendicular to the breastbone on flying birds that
Speaker 1: the pictorial muscles attached to, and they have reduced four
Speaker 1: limbs arranging from nearly absent in the Kiwi bird, to
Speaker 1: still obvious but reduced in size in the ostrich However,
Speaker 1: there are many ways the particular convergent traits can evolve.
Speaker 1: We spoke with Tim Sackton, director of bionformatics at Harvard.
Speaker 1: He said, before genomics, one could use developmental tools to
Speaker 1: figure out if the same or different developmental mechanisms seemed
Speaker 1: to be involved in convergent phenotypes. But the idea of
Speaker 1: levels of convergence same mutation, same gene or same pathway
Speaker 1: has developed in large part because it's possible to look
Speaker 1: in the genome for these things now. In the rabbites,
Speaker 1: for example, we were able to show that the same
Speaker 1: regions of the genome the control where and when certain
Speaker 1: genes are expressed, are repeatedly evolving in flightless birds. But
Speaker 1: this doesn't seem to involve the same nucleotide mutations. And yes,
Speaker 1: where some traits converge from completely different corners of the
Speaker 1: living world, the opposite is also true. Divergent evolution is
Speaker 1: the process by which groups from one species or organism
Speaker 1: begin to develop different traits, thereby splitting in two separate species.
Speaker 1: This often happens when populations of a species are separated geographically,
Speaker 1: and over time they adapt to the conditions of their
Speaker 1: new spot, whether it's increased predation pressures or a change
Speaker 1: in climate. One famous example of divergent evolution was found
Speaker 1: by Charles Darwin and has travels to the Galapagos Islands
Speaker 1: in eight thirty six. Darwin's finches, as they're now known,
Speaker 1: were a group of tanagers, which are not true finches,
Speaker 1: that lived on different islands in the archipelago, the main
Speaker 1: difference between them being the shape of their beaks, which
Speaker 1: changed over the generations due to the particular foods available
Speaker 1: to the birds on the different islands. And one more
Speaker 1: example fingerprints. Most non human animals don't have them, except
Speaker 1: for close human relatives such as chimps and gorillas, but
Speaker 1: koalas have fingerprints to The fascinating thing about human and
Speaker 1: koala prints is that, even though they're almost identical, they
Speaker 1: seem to have evolved independently. Today's episode was written by
Speaker 1: Jescelin Shields and produced by Tyler Clang. For more on
Speaker 1: this and lots of other converging and diverging topics, visit
Speaker 1: how stuff works dot com. Brain Stuff is a production
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