First Human Ancestor Looked Like a Squirrel
This tree-dwelling animal saw the dawn of an era when mammals would come to dominate the planet.
By Jennifer Viegas
Fri Oct 19, 2012 02:15 PM ET

Given its size, color and bushy tail, Purgatorius, illustrated here, almost resembles a modern-day squirrel.
by Douglas Boyer

Newly discovered fossilized bones for the world's oldest and most primitive known primate, Purgatorius, reveal a tiny, agile animal that spent much of its time eating fruit and climbing trees, according to a study.

The fossils, described today in a presentation at the Society of Vertebrate Paleontology's 72nd Annual Meeting in Raleigh, North Carolina, are the first known below-the-head bones for Purgatorius. Previously, only teeth revealed its existence.

"The ankle bones show that it had a mobile ankle joint like primates today that live in trees," co-author Stephen Chester, a Yale University vertebrate paleontologist, told Discovery News. "This mobility would have allowed for rotating the foot in different directions as it adjusted to different angles presented by tree trunks and branches."

PHOTOS: Faces of Our Ancestors

"It also shows that the first primates did not have elongate ankles that you see in many living primates today that are thought to be related to leaping behaviors," added Chester.

He conducted the study with colleagues Jonathan Bloch of the Florida Museum of Natural History and William Clemens, a professor emeritus at the University of California at Berkeley and a curator for the university's Museum of Paleontology.

...continues...

First human ancestor? *cringe*

Anyway....

First/oldest mammalian ancestor, perhaps?

I think they mean primate like, still very awkwardly phrased and misleading to those who might not know better.

"First ancestor" is even worse than "missing link"

Horwood Beer-Master wrote:"First ancestor" is even worse than "missing link"

Yeah! Taken literally, it means that the first living cells looked like squirrels!
Perhaps they mean the basal primate looked like a squirrel.

As squirrels are rodents (the earliest extant mammal group), it would not be at all surprising if the first primates looked like squirrels.

And according to this, primates branch off from rodents pretty late, after the carnivores and cows and stuff. It all comes back to stuff.

A significant detail of MOST squirrels is that, like early primates, they are arboreal. Getting around among the branches of a tree is assisted by having forward facing eyes, giving binocular vision, enabling bolder jumps. However, squirrels' eyes are not significantly forward facing, though there could be a limited area of binocular vision, at least in some species (what little information I can find on this subject on the internet is contradictory, perhaps referring to different squirrel species). Thus, the evolution of a squirrel-like rodent to a squirrel-like primate would involve the flattening of the face (so that the eyes do not point in such different directions), enabling the animal to jump around in the trees better.

The following PNAS paper emphasises another, perhaps even earlier adaptive strategy for the rodent-becoming-primate: manipulation of food plants:
Binocularity and brain evolution in primates
Obviously, once you have an area of binocularity, it has big implications, not only for your locomotive abilities, but for the structure of a visual cortex that has to support it.

DavidMcC wrote:As squirrels are rodents (the earliest extant mammal group),..

Huh? In what sense are they the earliest extant mammal group?

Ohh I thought it was slime

DoctorE wrote:Ohh I thought it was slime

Mammalian slime, eh?

Horwood Beer-Master wrote:

DavidMcC wrote:As squirrels are rodents (the earliest extant mammal group),..

Huh? In what sense are they the earliest extant mammal group?

I was forgetting about monotremes and marsupials, OK?
EDIT: I should have said earliest Eutherian mammals.

The first human ancestor looked like a complex polymer.

CdesignProponentsist wrote:The first human ancestor looked like a complex polymer.

Yeah, we've already been over that, CdP, but I wanted to make the thread more interesting, by re-interpreting the journalistic blunder to mean something more sensible - in fact, what I suspect it was intended to mean.

Yeah, I get what they meant. Just tossing another log on the fire

DavidMcC wrote:

Horwood Beer-Master wrote:

DavidMcC wrote:As squirrels are rodents (the earliest extant mammal group),..

Huh? In what sense are they the earliest extant mammal group?

I was forgetting about monotremes and marsupials, OK?
EDIT: I should have said earliest Eutherian mammals.

But even then, there are a number of groups that split from the Eutherian lineage before rodents did.

Horwood Beer-Master wrote:

DavidMcC wrote:

Horwood Beer-Master wrote:

DavidMcC wrote:As squirrels are rodents (the earliest extant mammal group),..

Huh? In what sense are they the earliest extant mammal group?

I was forgetting about monotremes and marsupials, OK?
EDIT: I should have said earliest Eutherian mammals.

But even then, there are a number of groups that split from the Eutherian lineage before rodents did.

Are you sure? Which ones, and is it undisputed?
EDIT: Actually, it doesn't really matter if there were other mammal groups splitting before rodent, the point is that we are primates, and primates split more-or-less directly from rodents at some stage. Of course there is always the possibility of ambiguity of classification of extinct species.
ANOTHER EDIT: Perhaps the shrews split before rodents, but so what? We aren't shrews, anyway.

... OK, maybe we ARE shrews ( ), or at least close. It's hard to get reliable info. on shrew vision, but they could be closer to primates than are the rodents.

DavidMcC wrote:

Horwood Beer-Master wrote:...But even then, there are a number of groups that split from the Eutherian lineage before rodents did.

Are you sure? Which ones, and is it undisputed?..

The earliest living groups to split off were the Xenarthra (sloths, anteaters and armadillos) and the Afrotheria (tenrecs, hyraxes, elephants, aardvarks and a few others); there is some dispute which order these two split off (or whether they split from the other Eutherians before splitting from each other), although I believe the Xenarthra are normally seen as splitting off first. Only after this do the Euarchontoglires (containing rodents and primates) split off.

DavidMcC wrote:...the point is that we are primates, and primates split more-or-less directly from rodents at some stage...

Actually, rodents split from their common ancestor with lagomorphs only after the split with the ancestor of primates; and similarly after splitting from the ancestor of Glires (rodents + lagomorphs) our ancestors were later to split from the ancestor of tree shrews, then later the ancestor of colugos.

The supposed "squirrel"-like creature described in the article is more closely related to us than to colugos; and therefore more closely related to us and colugos than it is to tree shrews; and therefore more closely related to us, colugos and tree shrews than it is to rodents; who in turn are more closely related to lagomorphs than they are to us, colugos, tree shrews or the "squirrel"-like creature described in the article.

DavidMcC wrote:... OK, maybe we ARE shrews ( ), or at least close. It's hard to get reliable info. on shrew vision, but they could be closer to primates than are the rodents.

It may be useful to understand that the name "shrew" is applied to a number of different not-particularly related groups of mammals, based on a purely superficial resemblance. Tree shrews are closer to primates than the rodents are, but tree shrews have nothing to do with the kind of shrews you may find in your garden in Europe.