July 8, 2012 | David F. Coppedge

Eats Shoots and Leaves

This is not a crime story, but a story nonetheless.

The latest human evolution star, Australopithecus sediba, ate leaves, according to its publicist, Lee Berger.  In Nature News on July 5 (Margaret J. Schoeninger entertained the idea, giving credit to the star behind the star, the father of evolution:

In 1871, Charles Darwin proposed that our earliest ancestors lived in Africa alongside the ancestors of today’s gorillas and chimpanzees, and ate a diet of fruit, leaves, seeds and nuts, similar to that of these extant primates. More recently, however, an alternative hypothesis has taken precedence — that the human lineage split from the apes in part as a result of our ancestors’ ability to obtain foods in open habitats, such as grasslands and savannah woodlands, that emerged in Africa following climatic changes during the Late Miocene epoch approximately 7 million years ago. These foods included grasses, sedge plants, grass-eating insects and small animals. On page 90 of this issue,1 Henry et al. present evidence that our early relatives had a more diverse diet, and ate items such as fruits, leaves and bark. The findings will trigger a rethink of the selective pressures that resulted in the separation of the ape and human lineages, and the traits we now consider to be unique to each.

Any paleoanthropology discovery failing to “trigger a rethink” would break tradition (trigger?  Remember, this is not a crime story).  Berger gave Amanda Henry the limelight as first of 9 authors of the paper,1 but Au. sediba is his baby.  Whether his baby ate leaves and bark from trees is less interesting to most readers as whether it belongs on the human family tree at all.  Scheoninger barked about some of the uncertainty involving bigger issues than just diet:

The significance of these results extends beyond whether a diet based on C4 foods is a fundamental hominin trait. It also brings into question our understanding of the evolution of bipedalism — another trait that is thought of as being fundamentally human. The species in which bipedalism emerged, and the evolutionary pressures that drove this adaptation, remain topics of debate….

How does the suggestion of dietary variation among hominins fit with this understanding of bipedalism and the branching of hominin species? Researchers have suggested that there was an adaptive radiation event approximately 2 million years ago, in which a common ancestor relatively rapidly gave rise to a range of bipedal species with novel traits that allowed them to move into new habitats. The unexamined assumption that all bipedal species share a unique genealogical relationship is reminiscent of evolutionary biologist Stephen J. Gould’s question: “What, if anything, is a zebra?”. Gould examined whether the three species of modern zebra are more closely related to one another than to other non-striped horse species. He concluded that striping evolved only once. We should also ask: what, if anything, is a hominin? Perhaps all ancestral ape-like species that walked on two legs and had a C4-focused diet were uniquely related to each other but were not necessarily human ancestors. Maybe humans emerged from some other hominin groups around 2 million years ago that were also bipedal and had more general, opportunistic foraging strategies, including meat-eating. Only enterprising studies into other aspects of australopithecine and hominin life, like Henry and colleagues’ analysis of Au. sediba‘s diet, will provide us with definitive answers.

Since definitive answers are lacking here, readers might like to look elsewhere.  One place to look is Discovery Institute’s latest book, Science and Human Origins by Ann Gauger, Douglas Axe and Casey Luskin, announced June 20 on Evolution News & Views (see lengthy review at ENV June 25).  A later post on Evolution News & Views by David Klinghoffer described one chapter by Luskin that presents the appearance of the genus Homo as a “big bang” reminiscent of the Cambrian explosion.  Postulating ape-like australopithecines to be human ancestors is “plagued with problems,” Luskin’s research survey revealed, a fact that the media “labor to obscure”.  Particularly, Au. sediba presents evolutionary tree problems, Klinghoffer commented in another post on Evolution News & Views: a diet of bark and leaves makes it less hominin-like and more ape-like than Berger wants. So if Au. sediba eats shoots, barks and leaves, is Berger barking up the wrong tree?

Click here for ENV’s list of articles about Science and Human Origins.  If Darwin led evolutionists down the primrose path for over 140 years, that would be a crime.

1. Henry et al., “The diet of Australopithecus sediba,” Nature 487 (05 July 2012), pp. 90–93, doi:10.1038/nature11185.

“Eats shoots and leaves” is a humorous phrase teachers use to point out the importance of punctuation to understanding (is it about a criminal or a koala?).  But even if we take Berger’s meaning, it doesn’t mean he has understanding: especially if, after 141 years, Darwin’s tribe of forensic investigators still has to stuff their understanding in the pigeonhole labeled “things to do tomorrow.”  We wonder what kind of “enterprising studies” Scheoninger has in mind.  If history is any guide, the Darwinian form of “enterprising studies” belongs at Comedy Central, where they try to keep you laughing but never serve the beef; just empty promises that further studies will provide understanding. Shoot; make like a tree, and leaf for a real burger joint.



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