[OT] Species and identification

[Heretic Apostate]

I'm watching Walking with Prehistoric Beasts, and I see all these strange creatures. I see a waddling four-legged creature, and am told that this is an ancestor of whales. I see something that looks like a cross between a gorilla and a sloth, and am told that this is an ancestor of horses.

Okay, HOW do they do these identifications? How do they decide that these are similar species?

(Keep it as layman as possible. Highest biology was high school freshman biology, and I didn't have fun in that class...)

 

[DWARF]

Okay.... as simple as possible, eh...

They have lots of fossils. If you line some of them in a row, the bones look similar. Sort of like if you had class pictures for a child, going from grades 1 to 12. Each picture is similar, but the child has differences. With enough pictures, or fossils for scientists, you can judge that the person in grade 12 came from the person in grade 1. Same thing with prehistoric animals and lineages of animal fossils.

 

[Jeremy Ackerman-Yost]

Well, a lot can be learned from the morphology of the skeleton and skull. For example, you can group animals based on the fact that all of their toes have fused into a hoof. And then as you go a little further back in the fossil record, you find a similarly shaped critter, where only three of the toes are fused, and there are a couple little dangly useless toes on the back. And when you go further and further back in a stepwise fashion, you come to a critter with regular paws.

Same thing with whales. The further you go back, you eventually encounter a whale-like critter whose limbs still look more like legs than paddles, but are still off to the side, like whale limbs. You find this critter in coastal areas. You dig a bit deeper, and further inland, and you find a similar critter whose legs are sturdier, and slung more underneath.

Once you've catalogued sufficient similarities and differences, you can start to make some guesses about the family tree. As you gather more and more data, the possibility of error gets so low as to be negligible, and you have a working hypothesis.

 

[Heretic Apostate]

Okay, makes a bit more sense. I guess I'm mostly confused because I'm watching what's basically the beginning (more or less), and trying to see how two species can be related, not taking into account 40+ million years of evolution.

Still, seems strange to see a sloth/gorilla being called a horse.

 

[Jeremy Ackerman-Yost]

Still, seems strange to see a sloth/gorilla being called a horse.

Well, if you go far enough back, all us mammals started out as something like poorly evolved shrews. Slightly reptile-ish poorly evolved shrews, for that matter.

 

[Tonguez]

Well, if you go far enough back, all us mammals started out as something like poorly evolved shrews. Slightly reptile-ish poorly evolved shrews, for that matter.

Well that does depend on the theory of species adaption and modification you adhere to.

As for me whilst I'm okay with a Gorilla-Sloth (it would make a great monster btw) being called a horse, I'm not convinced about the relationship between the Hyrax and the Elephant based on the fact that they have similar toes!

 

[Jeremy Ackerman-Yost]

Point taken. It's a pretty muddy field, all around.