House-husbands. Not so progressive after all…

A terrific paper in Nature this month used an ingenious combination of strontium isotope analysis of molars from individuals of the species Australopithecus africanus and Paranthropus robustus and comparisons of molar size as indicators of sex (much greater sexual dimorphism in these early hominins) to come to two very interesting conclusions.

1) It would appear that in our early bipedal ancestors, and indeed cousins in the case of P. robustus,  it was more common for females to disperse from their place of birth and ally themselves with other ‘troops’ (for want of a better word) than it was for males. Males it would seem, enjoyed something of a ‘stay at home father’ lifestyle and had only relatively small ranges. This is in agreeance with what is seen in many modern human societies and those of our close extant relatives like the chimpanzees and bonobos (but not gorillas or other primates).

2) With the above point in mind, this challenges the notion that bipedalism evolved as a consequence of an increased need to move long distances, the so-called ‘endurance’ theories. Given my personal leanings toward the wading model put forward by Niemitz in Naturwissenschaften in 2007 and general unease with the unconvincing evidence for the endurance models I found these findings in Nature both exciting and in the best possible sense unsurprising.

There are of course other interpretations that are possible, such as the small home range being an example of a preferred habitat (cave-dwelling). If this were the case the species in question may roam further under more general circumstances but I find that unlikely. I anticipate that future evidence will support the ‘small range’ idea above as a general behavioural truth about our ancestors.

Citation:

“Strontium isotope evidence for landscape use by early hominins”

Copeland, S., Sponheimer, M., Ruiter, D., Lee-Thorp, J., Codron, D., Roux, P., Grimes, V. & Richards, M.

NatureVolume: 474, Pages:76–78 Date published:(02 June 2011)

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~ by confusedious on June 2, 2011.

2 Responses to “House-husbands. Not so progressive after all…”

  1. Good to know, and I’m thankful I don’t have to rewrite my characters. In the first book of the series, I deal primarily with Homo habilis, but since s/he co-existed with Australopithecines, I had to add that immediate precursor to Homo in supporting roles. I have the male finding a female mate from another band. My research seemed to validate that conclusion and now you have, too.

    Good news. Of course, there’s the whole home base controversy for both species. We can chat about that later.

    With the exception of some evidence in South Africa, I haven’t seen convincing proof that Australopithecines or Homo habilis lived in caves. I put my characters against a cliff wall, away from a nearby lake. Have I missed some findings?

    • Some of the remains used in this strontium isotope analysis were found in and around cave systems. This, however, doesn’t necessarily suggest caves as the primary habitat of either of these species, it could simply be a case of a small population making use of these landforms as a convenience. Through the retrospective eye of evolutionary psychology though, I tentatively suggest that hominin use of caves or similar geological shelters (against a cliff wall as you suggested) is quite ancient indeed. The use of such shelters is quite ingrained into our behaviour, what is a house but an artificial cave? Many of our later Homo ancestors, as you most likely know, most certainly did make use of caves and rock formations, I don’t think it’s too extreme a stretch to push this usage back further in time. After all, Australopithecines weren’t all that well equipped to protect themselves from predators, or even run away from them, some type of shelter would have made sense (heading up trees is another strategy, but the degree of arboreality maintained by Australopithecines is still a topic of debate).

      I’d say you’re still on track with the cliff face, so I wouldn’t worry.

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