The tree of life is HUGE. HUGE. According to a draft described in the journal Proceedings

of the National Academy of Sciences. The latest draft of the great tree named over 2.3 million

species of animals, plants, fungi, and bacteria. Previous versions of the tree of life only

charted about 100,000 species. But this new HUGE tree is truly an awesome sight to behold.

To get a close up look at the whole thing check out https://tree.opentreeoflife.org.

There’s a link in the description.

But that got me wondering, with millions and millions of species on this planet. How do

we tell them apart?

Evolution is a beautiful thing. The branches of life spread out in every direction as life

finds a way into every niche imaginable. A new species arises in a process called speciation.

It’s when something happens to separate it from all that came before, like a new trait

or geological isolation.

Naturalists like Charles Darwin used to tell species apart the old fashioned way. Just

by lookin’ at em, which is called morphology. It’s telling species apart by their appearance.

But there’s another way to define a species, biologically. I’ve often heard a species

defined as animals that can reproduce and make a viable, fertile offspring. Basically

if two animals can make a baby that lives and can later make it’s own baby, then those

two animals are the same species.

Which is basically what the Biological Species Concept (BSC) says. This concept was introduced

by biologist Ernst Mayr in the mid-20th century as "species are groups of interbreeding natural

populations that are reproductively isolated from other such groups."

But both of these definitions aren’t perfect. Life finds a way. So sometimes creatures that

look wildly different can breed. Like take dog breeds for example. If you were an alien

taxonomist coming to Earth for the first time, you might be very confused by how all these

creatures, from the smallest to chihuahua to the greatest Dane could possibly be the

same breed.

On the other hand a group of animals that look an awful lot alike can actually be different

species. In some cases different species evolved similar traits because they’re in similar

environments like Fossas and cats, which cannot reproduce. Or different species might be closely

related and look a lot alike but can’t produce fertile offspring. Like horses and donkeys.

Sure they can produce a hybrid called a mule, but they’re sterile.

But even on a finer level, sometimes scientists get a surprise and find that different species

might not be so different after all. And that’s just the trouble a group of scientists in

Australia ran into. In a study published in the journal Biology Letters researchers found

that different species of Rock-Wallabys were swapping DNA!

Six different species of rockwallaby were thought to be separate species because the

way their genetic material package would stop an offspring from being fertile. But upon

genetic analysis the researchers found gene flow between the species, suggesting something

else was going on, forcing them to rethink their evolution. This finding suggests that

these animals were getting it on, making babies that could make some more babies. The rock-wallabies

might not be “reproductively isolated”, possibly meaning they were more like a single

species than previously thought.

Like in the case of these rock-wallabies scientists could see a species’ history written in

its DNA. Thanks to modern technology, molecular genetic sequencing changed the game in biology.

By comparing the DNA of different animals, scientists can see how they’re related or

not. This was a huge advance in the field of taxonomy. It’s how we know our closest

cousins are chimps and bonobos, if we went by morphology alone, perhaps we’d think

orangutans were our next of kin.

According to a study published in the Journal of Biogeography we share more physical features

with orangutans, like beards on men and similar shoulder blades. But molecular genetics revealed

we share only 97% of our DNA with them and 99% with chimps and bonobos.

So it can help us not just learn about the rest of world, but taxonomy helps us find

our place in the animal kingdom too. Some people think taxonomy and naming species is

dumb, because it does seem somewhat arbitrary. I mean humans are the ones deciding where

those lines between species are. But I think it’s really important. Because humans need

to categorize things to make sense of this crazy, chaotic world. and it’s so important

to keep track of all the diversity of life on this planet, while it’s still here. There’s

a real risk we’re losing species before we can even find them. So no, taxonomy isn’t

perfect. But it’s the best we’ve got.

Taxonomy helps us know our history, like when recently scientists announced the discovery

of yet another human-like ancestor. So Julian asked the question, how do we determine if

they belong to the genus homo in this great episode right here.

Alright friends, if you haven’t heard the news yet, WE’RE DOING A LIVE SHOW. RIGHT

HERE IN SAN FRANCISCO! I’M SO EXCITED! We’ve got a great line up of all your favorite hosts.

I’ll be there, trace will be there Julian, Amy and Crystal will be there and so so many

more special guests like Dr. Joe Hanson from It’s Okay to Be Smart and Brian Brushwood,

magician, TV personality, host of Scam School, Anthropologist Natalia Reagan, and Dr. Carin

Bondar, Discovery Channel host and TED presenter.

It’s all going down October 22. So grab your tickets before they’re gone. there’s

a link in the description.