Orangutans: our closest relative?

A few weeks ago an interesting and outlandish claim came to light in the scientific literature [1]. Jefferey Schwartz and John Grehan, two taxonomists from  Pittsburgh and New York respectively published a paper claiming that Orangutans are our closest relations, not chimps, as we commonly accept.  Having a ginger fioncee, I have long held that she is closer to an Oragnutan than a girlfriend, but that is perhaps beside the point. Are all of us a lot closer to the ‘old men of the forest’ than we would like to think?

Jeff Schwartz

Jeff Schwartz

So what’s the back story to this controversial claim? Well, ever since Jared Diamond’s acclaimed work The third chimpanzee [2] people have accepted it as alomst a common sense fact that we humans are most closely related to chimpanzees. Popular belief is that we share a common ancestor with an assortment of monkey-type creatures, but that ourselves, chimpanzees and bonobos (despite these creatures having a slightly strange name, they are almost indistinguishable from common chimps) are all on the same arm of the family tree, so to speak. Gorillas and Orangutans have been held somewhat uncomfortably at arms length – we believe they represent an earlier split from the primate evolutionary lineage. Of course, the evidence of DNA backs this up very nicely, and indeed, there appears  little reason to question it. The evidence goes someting like this:

% of DNA that is identical to that of humans 3]:

Common Chimpanzee – 98.4

Gorilla – 97.5

Orangutan – 96.5

Well that would seem to tie it up rather tidily. These ‘crazy’ Americans argue though, that just because two species have more similar DNA does not mean they are more closely related. How could that be?

This guy could be your cousin, 1,023,760,007 times removed.

This guy could be your cousin, 1,023,760,007 times removed.

What could have happened is that humans and orangutans split apart relatively recently from the shared ape ancestor as compared to chimps, but for one reason or another (say each species re-locating to a vastly different habitat),  one species evolved extremely quickly, and  now has noticeably different DNA.

This is fine as a hypothesis – despite the fact that most scientists appear to be sneering at it – as there is no way to refute it with evidence, no matter how unlikely it may seem. But do Schwartz and Greham have any reasons why they think their alternative human history, is more likely than the critically accepted version, aside from just postulating that DNA-based evidence isn’t up to much?

In fact yes, they do. Their arguments come down to anatomy and behavior, which they state are much more similar between humans and orangs than the other apes. For example, among the great apes only humans and Orangutans have facial hair in males, thick tooth enamel, an ability to construct shelters and a preference for private mating.

Many scientists are upset that these kind of outlandish and potentially unsubstantiated claims have been published at all. On the contrary though, isn’t it vital that these kind of claims are aired? Who knows if this idea is right (I would argue that, actually, we may never) but it’s important that they come to light and we think about them. As scientists we need to be able to accept that the only thing we can ever be sure of is that we don’t know it all. Let’s try though, and let’s not always assume we have the answers already.

One thing I am sure of though – my girlfriends DNA must be at least 97% forest-based. I don’t care what you say.


[1]Read the abstract (or whole paper if you have access) here.

[2] The third chimpanzee: the evolution and future of the human animal was an all-encompassing book by American thinker and scientist Jared Diamond. A bit of a Richard Dawkins of his day,  Diamond wrote prolifically about how humans had evolved from apes and managed to convince whole swathes of the population.

[3]  These figures come from a recent New Scientist report on this new theory.

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One Response to Orangutans: our closest relative?

  1. Pingback: Want more scientists? Make school classes relevant to pupils lives. « Bench TwentyOne

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