Posted by: paulgarner | August 25, 2010

Is sediba human?

The critics are really gunning for Todd Wood following the publication of his baraminological analysis which controversially suggested that Australopithecus sediba should be included within the human holobaramin. Peter Line and Marvin Lubenow were the first to wade in and now David Menton, Anne Habermehl and David DeWitt have offered ARJ readers their thoughts. All these authors agree that sediba is not and cannot be a member of the human holobaramin, and express this view rather forcefully. Like Todd, I must admit to being somewhat baffled by the strength of feeling that this study has obviously provoked. Here are a few thoughts of my own on the issue:

1) The critics seem very unwilling to expand their concept of human morphological variation to include sediba. But it would be a mistake to assume that the range of variation that we observe within modern humans is necessarily representative of the range of variation in the past. If we are willing to include Homo sapiens neanderthalensis, Homo erectus and Homo ergaster within the human holobaramin – as at least some of Todd’s critics do – then we have already allowed that the range of morphological variation was much wider than today. In which case, why exclude a taxon with sediba-like morphology a priori?

2) The critics appear ready to reject statistical baraminology in toto because it yields an unpalatable conclusion with respect to sediba, but they do not offer any alternative ideas about how we might identify baramins among extinct taxa known only from the fossil record. It is not adequate to say, as Habermehl does, that the Bible already tells us that some fossils are humans and others are not. We are interested in the status of individual taxa, sediba included, and the Bible yields no information about the humerofemoral indices (or other skeletal characteristics) of early post-Flood humans.

3) In all their fulminations, the critics have apparently overlooked the tentative nature of Todd’s conclusions. It is certainly difficult to see how Peter Line got the idea that Todd was presenting statistical baraminology “as some kind of a ‘be all and end all’ human-australopith ‘truth detector'”. The discussion in Todd’s original paper is hedged about with all kinds of provisos and explicitly draws attention to the limitations imposed by the available data sets and methods of analysis.

Personally I am somewhat agnostic concerning the baraminological status of sediba. I was surprised that sediba appeared to cluster with humans rather than with the australopiths, but understand that further studies utilising more holistic datasets may well paint a different picture. I remain willing to consider and evaluate different hypotheses, but it seems to me that the response of Todd’s critics so far has been really quite irrational and far too reactionary.

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