Giraffes on the brain

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The evolution of giraffes has been on my mind quite frequently as of late, although it's been difficult tracking down information about the evolution of the group (it was once much more diverse than it is today, a trend also illustrated by elephants and horses). Along the way, though, I've turned up a few interesting papers involving the ever-vexing question of how the long neck of the giraffe evolved, the first being a letter to Nature by Chapman Pincher published in 1949. Criticizing Darwin's hypothesis that giraffes evolved long necks to reach higher levels of vegetation during droughts, Pincher proposes that the giraffes were naturally selected to have long legs to escape predators, the neck requiring lengthening if the giraffe was going to be able to drink with such long limbs;

Now, like other ruminants, the giraffe requires a plentiful supply of water. The development of an increasing shoulder height, therefore, necessitated the development of a means of getting the head down to water-level. Horses and antelopes solved this problem by the simultaneous development of a proportionately long neck. I believe the giraffe solved it in the same way. That the neck has elongated to a degree only just sufficient to keep pace with the increasing length of the legs is suggested by the fact that the giraffe has to splay its forelimbs awkwardly to drink.

In a reply that came in August of that same year, E. Robinson said that Pincher's hypothesis was no more reasonable than Darwin's (zebras, for instance, developed speed without taking on a giraffe-like form);

If the excessive length of the fore-legs has been developed to give increased speed, it seems rather odd that the hind-legs did not lengthen in the same proportion. If we accept Darwin's theory, we should naturally expect to find an increase in the length of the fore-legs, as otherwise, other measurements being as they are, the animal would have to balance on its hind-legs in order to maintain its present head height while eating.

Such conjectures are made all the more problematic in that they are trying to take the form and natural history of a living animal and extrapolate backwards in a kind of evolutionary uniformitarianism; without older fossil relatives, we could come up with numerous hypotheses that might seem just as reasonable as any other. Indeed, it is all too easy to fall into constructing hypotheses about what a giraffe's neck evolved for rather than trying to figure out what factors influenced its evolution over the course of millions of years.

Of further interest is a 1936 paper by Edwin Colbert published in the journal American Anthropologist about whether the extinct giraffid Sivatherium was known to people living in present-day Iraq about 5,500 years ago. Colbert's evidence is a copper rein-ring on which some sort of ruminant animal is depicted, but according to Colbert the horn shape did not match any of the antelope or other animals in the area at the time.

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A comparison of the copper figure and a reconstruction of Sivatherium. From Colbert's 1936 paper.


The resemblance is striking, but as far as I've been able to tell Colbert's hypothesis was not further researched. It is possible that the figure pictured above is an early artistic restoration of a strange, extinct giraffe, but I am not in a position to either confirm or deny Colbert's idea.

More like this

I would love to see Edward Colbert defend his paper of The Colbert Report.

Incidentally, David W. Anthony Professor of Anthropology at Hartwick Collge, has written a book called:
"The Horse, The Wheel, and Language
How Bronze Age Riders from the Eurasion Steppes Shaped the Modern World".

I'm thinking I should send him a link to this - could be something there.

I am intrigued by two articles with the same title, "Winning by a neck", published on the same journal, The American Naturalist.

The first (Simmons and Scheepers 1996) makes the hypothesis of sexual selection. The second (Cameron and du Toit 2007) restates the case for competition in foraging. I am puzzled.

Not on topic but I see your new banner is less feisty than your old one. I hope this isn't a bellwether for your writing style. I like your feisty blogs!

On Colbert and Sivatherium...
Colbert tells the story in his autobiography: the chapter is headed by a life reconstruction of S. by Margaret Colbert that I think has potential as a Christmas card...
...
As for further research, Christine Janis wrote an article about it in the journal "Cryptozoology". I haven't seen it.

By Allen Hazen (not verified) on 03 Mar 2008 #permalink

Thanks, Allen. I picked up Colbert's autobiography and, sure enough, it's in there. Unfortunately not much is said about it, but I'll ask around a bit and see if I can turn up anything else.

(it was once much more diverse than it is today, a trend also illustrated by elephants and horses)

- and Hominids!

Hmmm...the resemblance is remarkable...but assuming that reconstruction was drawn with Colbert's hypothesis in mind it might be a fairly circular line of evidence. Presumably some Sivatherium remains in an archaeological context is the only way to be sure, but it's worth noting that extra horns are pretty common among domestic ruminants, although perhaps they don't usually manifest themselves on the frontal as apparently shown in the figurine.

Presumably, Adrienne Mayor would suggest that the Babylonian artist was inspired by a fossil skull, perhaps a more reasonable hypothesis than Colbert's minus any corroborating evidence for a relict population of Sivatherium.

Unfortunately, I think artistic license is a profound difficulty when trying to ascribe biological significance to artistic representations. It's easy to imagine scholars 1000 years from now trying to say Demoiselles d'Avignon is compelling evidence for extreme fluctuating asymmetry among early 20th C. French prostitutes, or perhaps extreme pathology induced by STIs..

just sayin.

Neil; You may be right. I wish there was some more information (especially on the distribution of Sivatherium and where it persisted and until when, as I've seen unreferenced dates for extinction at 5,000 years ago) but it's likely that this artifact will remain a curiosity.

Given the arrangement of the horns (the broad horns on the side, the two projections pointing toward the midline, and the horns more towards the front) I think there's a good chance the art was inspired by a Sivatherium rather than domestic ruminants. Like you said, though, I'd have to see some actual Sivatherium skulls as most of what I've come across so far have been restorations.

If anything I think Colbert's paper serves as a clue or a data point that needs more research, but honestly I don't see much resolution coming to the issue given the state of affairs in the area in which the figure was found.

I believe that paleontologist Christine Janis has published a paper on the possibility that the Sivathere is depicted in artifacts from Central Asia.

By Adrienne Mayor (not verified) on 11 Mar 2008 #permalink

Christine Janis, "Fossil Ungulate Mammals Depicted on Archaeological Artifacts" Cryptozoology 6 (1987): 8-23, with useful illustrations.

Janis discusses Colbert's paper of 1936, and possible depictions of Bramatherium on other Eurasian artifacts, possible representations of chalicotherium, Pliohyrax, and Mesimbroportax in artifacts from Siberia, China, and Africa, respectively.

By adrienne mayor (not verified) on 11 Mar 2008 #permalink