How Far Back In The Human Family Tree Do You Have To Go

[Gelatinous squid]

before you find an ancestor that is fully quadrupedal? I think the last fully quadrupedal primate ancestor probably lived with the dinosaurs, yes?

[Seldom]

No!!

[Auspex]

I think, by definition, a "fully quadrupedal" 'primate' would have to be ancestral to primates, since true primates employ a range of locomotor behaviors. And, I think that ancestor would have occurred in the Paleogene (post-dino).

[Wakaritai]

You made me curious. At first my opinion was identical to Auspex's, but after doing a bit of googling they go back pretty far. Here is a quote (from wikipedia):

"According to fossil evidence, the primitive ancestors of primates may have existed in the late Cretaceous period around 65 million years ago, and the oldest known primate is the Late Paleocene Plesiadapis, c. 55–58 million years ago. Molecular clock studies suggest that the primate branch may be even older, originating in the mid-Cretaceous period around 85 mya."

Now that doesn't necessarily answer your question. That is regarding the oldest known primates, not the most recent fully quadrupedal ancestor that eventually evolved into a species of primate. That is, unless all primates come from a common ancestor and only fairly recently (last couple million years) branched out. And if the latter is not the case, you might have to be more specific, because there may be different answers for different species.

But that is still talking about small primates (rodent-sized), not the larger primates that we have now. For primates to come to power like we did, we needed the dinos to go extinct, preferably while we were small enough to survive. Lucky us

[siteseer]

On 3/28/2010 at 10:31 AM, Wakaritai said:

You made me curious. At first my opinion was identical to Auspex's, but after doing a bit of googling they go back pretty far. Here is a quote (from wikipedia):

"According to fossil evidence, the primitive ancestors of primates may have existed in the late Cretaceous period around 65 million years ago, and the oldest known primate is the Late Paleocene Plesiadapis, c. 55–58 million years ago. Molecular clock studies suggest that the primate branch may be even older, originating in the mid-Cretaceous period around 85 mya."

Now that doesn't necessarily answer your question. That is regarding the oldest known primates, not the most recent fully quadrupedal ancestor that eventually evolved into a species of primate. That is, unless all primates come from a common ancestor and only fairly recently (last couple million years) branched out. And if the latter is not the case, you might have to be more specific, because there may be different answers for different species.

But that is still talking about small primates (rodent-sized), not the larger primates that we have now. For primates to come to power like we did, we needed the dinos to go extinct, preferably while we were small enough to survive. Lucky us

 

While looking through the most ancient threads of this category, I came upon this one concerning early primates.  First of all, Plesiadapis belongs to a suborder of mammals, Plesiadapiformes, which has been considered part of the order Primates and has also been placed separately.  It appears most mammal researchers are leaning toward them being primates or at least a sister group, that meaning that plesiadapiforms and euprimates (primates we are familiar with like lemurs, tarsiers, monkeys, apes, humans) have a common ancestor.  It certainly appears that they are at least very closely related to primates but only a couple of the known genera could be considered as possibly ancestral to primates (Rose, 2006: .

 

Plesiadapiforms are actually known from the early Paleocene and the earliest known genus, Purgatorius, was described as coming from the Late Cretaceous of Montana though the nature of the deposit (partly reworked Cretaceous material in an early Paleocene formation) put this in question to the point that most researchers appear to side with it being a Paleocene form.  Purgatorius and many other early Paleocene plesiadapiforms are known mostly from their teeth (though Purgatorius bones were documented just a few years ago, see Chester et al., 2015) and because it retains four lower premolars, Purgatorius could be ancestral to the earliest euprimates known that appeared later (Rose, 2006: 171).

 

The occurrence of Purgatorius at the base of the Paleocene, if not the latest Cretaceous, indicates that plesiadapiforms may be rooted in the late Cretaceous but it seems to have been just another lineage that sprouted as part of a great radiation of mammals at that time - forms that led to the diversity we know today competing with others that would die out by the end of the Eocene or even before the end of the Paleocene.

 

 

Chester, S. G. B., J.I. Bloch, J., D.M. Boyer, & W.A. Clemens.  2015. 

Oldest known euarchontan postcrania and affinities of Paleocene Purgatorius to Primates. Proceedings of the National Academy of Sciences, USA, 112, 1487–1492.

 

Rose, K.D.  2006.

The Beginning of the Age of Mammals.  Johns Hopkins University Press. Baltimore.  428 pages.

[ashcraft]

I suspect fully quad. would date to around the divergence of rodents, bats, and primates from each other.

Brent Ashcraft

[connorp]

On 3/28/2010 at 1:31 PM, Wakaritai said:

You made me curious. At first my opinion was identical to Auspex's, but after doing a bit of googling they go back pretty far. Here is a quote (from wikipedia):

"According to fossil evidence, the primitive ancestors of primates may have existed in the late Cretaceous period around 65 million years ago, and the oldest known primate is the Late Paleocene Plesiadapis, c. 55–58 million years ago. Molecular clock studies suggest that the primate branch may be even older, originating in the mid-Cretaceous period around 85 mya."

Now that doesn't necessarily answer your question. That is regarding the oldest known primates, not the most recent fully quadrupedal ancestor that eventually evolved into a species of primate. That is, unless all primates come from a common ancestor and only fairly recently (last couple million years) branched out. And if the latter is not the case, you might have to be more specific, because there may be different answers for different species.

But that is still talking about small primates (rodent-sized), not the larger primates that we have now. For primates to come to power like we did, we needed the dinos to go extinct, preferably while we were small enough to survive. Lucky us

I would like to emphasize that molecular clock studies should really be taken with a grain of salt.

[Mediospirifer]

I'd look to the divergence between apes and monkeys. In general, apes walk upright (exceptions being chimps and gorillas knucklewalking) and travel in the trees by swinging underneath branches, while monkeys are quadrupedal and run on all fours on top of branches. The monkeylike ancestor to modern apes would have been quadrupedal.

 

A quick Google search turns up this article (Livescience). This author reports that the genetic analyses suggest a split between 25-30 MYA, and a recent fossil find of a early ape relative dating to 25 MYA supports that.

 

This is a pop-science article, not the peer-reviewed paper. I haven't (yet) read the paper, but it's here: LINK.

 

Just my 2 cents...

[Mediospirifer]

I should add, the paper I referenced talks about fossil teeth and jaw fragments. It doesn't address the shoulder and hip structures of the critters in question.

 

It seems likely to me that both animals in the paper were fully quadrupedal, and bipedal locomotion in apes appeared sometime after that. So, 25-30 MYA is an earliest boundary for bipedalism.

 

In my opinion.