The Caveman’s Corner

This is Meet an Ancestor installment three: Leptadapis magnus. The subject here also dovetails nicely with the post I’m writing on the adapoid theory of anthropoid origins, though it was selected a while before the idea for the latter series came into my head.

L. magnus cranium

Why is it relevant? Because L. magnus is an adapoid, specifically a member of the European family of the Adapidae. And that gives me the opportunity to tell an interesting story.

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Anthropoid origins is likely the single subject dearest to my heart in all of science, so I thought I might want to lay out in a series of essays for the reader some of the basic controversies surrounding this fascinating but much under-covered topic. I’d also like the sharpen up my own knowledge a bit as I fear it has been slipping. I’ll begin here by laying some of the basic concepts and terminology of the debate.

Anthropoid diversity

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According to G. Reagan and C. Ross in a study published in Folia Primatologica 71 and reported in the latest issue of Current Anthropology, twins of Wied’s black tufted ear marmosets share a significant amount of genetic information while in the womb. They’re chimeras.

To quote the report:

Starting on the nineteenth day of development and ending by the twenty-ninth, the placentas of twins begin to fuse. During this time, the twins exchange stem cells that carry with them their genetic makeup, with the result that individuals possess both cells inherited at conception that contain the original DNA of their parents and other cells that contain the DNA of their fraternal twins. This pattern, known as chimerism, was found in all bodily tissues sampled, including reproductive gametes. In one instance, a female marmoset passed on her twin brother’s DNA to her offspring, making her children her genetic nieces or nephews.

This has implications for the marmoset pattern of child rearing which involves extensive parental investment, especially by the father.

Because of the stem cell exchange between twins, individuals in a marmoset family group may share more than 50% of their genetic information (the typical degree of relatedness between parents and their offspring or between siblings). This creates a situation in which family members may have more invested in their offspring or siblings than predicted for other species—a possibility that will greatly affect the present understanding of how genetics and behavior interact.

Marmosets aren’t just their brother’s keeper. They’re their brother’s father.

After a long hiatus, I bring you another installment of “Meet a Contemporary.” Yayyyyy. School’s out now, so this blog should pick up a bit.

Meet Callitrhix (sometimes Cebuella) pygmaea, or the pygmy marmoset, a contender with the gray mouse lemur, lesser galago, and pygmy tarsier for smallest living primate. They’re cute little buggers and often kept in private homes as pets in the West (not a practice primatologists are favorable towards). For those two reasons, the pygmy marmoset might well be familiar to the reader.

Awww.

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I have a question I would like to ask the world:

?

What is this supposed to be? There is no monkey that looks like that. There is no animal on earth that looks like that. Why is this (basically) what everyone thinks of when they hear “monkey”?

As far as I can figure out, it looks sort of like a cartoony chimpanzee (Curious George maybe?) with a tail randomly stuck on. Not that chimpanzees are that color. There are some macaques that have vaguely that color of fur by they all have bright colorations on their exposed skin. There aren’t that many brown monkeys, honestly. Maybe a spider monkey except the proportions are all wrong.

I guess that’s what those are. Fracked up, brown spider monkeys. I want to get an ethnozoologist onto how on earth that’s come to be the number one public image of “primate.” *sigh*

So the whole weekly thing is pretty much out the window. I’ve been experiencing some technical difficulties for a while and I’ve had other matters to attend to/lacked motivation. But, you may unbate your breath, we have Meet an Ancestor entry number two: Propliopithecus chirobates.

A reconstruction of Propliopithecus

Woohoo, we finally got our super-obscure species that Google hasn’t heard of (Did you mean: propliopithecus chorobates). It is, however, a member of a quite famous and extremely important lineage.

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We have a rant today.

I’ve been doing the research for my next “meet an ancestor” today, and I keep coming across one word, “Cebidae.” Apparently, the ecology of our ancestor’s genus was similar to that of the Cebidae. Well, that’s quite interesting, or at least it would be if I knew at all what the authors meant by Cebidae.

The debate we’re getting into here is over the macrotaxonomy of the New World Monkeys. Some authorities like to split it up into lots of little families, as many as seven, while some prefer to refer it in its entirety to one family, incidentally the Cebidae.

Thus, Walker’s Primates of the World, Stein and Rowe’s Physical Anthropology 8th ed., and the Pictorial Guide to the Living Primates give the Cebidae as 11 genera ranging from squirrel monkeys to spider monkeys; everything but marmosets and tarmarins. The Encyclopedia of Human Evolution prefers to exclude only the spider monkeys from the Cebidae and include the marmosets. Animal Diversity Web lumps in all the New World Monkeys. And finally, Wikipedia authoritatively states that the Cebidae is “one of the four families of New World monkeys now recognised,” and is a combination of marmosets, squirrel monkeys, and capuchins (the actual genus Cebus).

Cebus, about the only member of the Cebidae everyone agrees on

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Sorry I haven’t been being terribly faithful with these “Meet a …” things, but I’ve been otherwise engaged for the past week or so. Our very first Meet a Contemporary is at once easy and hard to compose a profile on: Easy because it’s an orangutan and you can find about anything you want on it, but hard because it’s an orangutan and anyone who’s ever watched a nature show knows all the basics already, so it might be a bit difficult to make this interesting.

Meet, the Sumatran orangutan (or orang-utan for our Commonwealth readers).

A P. abelii in the type of suspensory posture typical of the orangutans.

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As I rather suspected would be the case, our very first “Meet an Ancestor” ancestor isn’t strictly a human ancestor. More of an extinct, collateral cousin. It is, however, a fairly well known species on which there is a good amount of information. I was afraid I’d get some obscure Plesiadapid that didn’t even register on Google.

T. oswaldi reconstruction from DKimages

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This will have the same idea as Meet an Ancestor, except I’ll use A Pictorial Guide to the Living Primates. So, look forward to that too.