Thursday, February 21, 2008

Coupla paleo- and bioanth stories Both via Hawks:

First, some discussion on the out of Africa analysis (see here).

Second, on hygienic dating (not what you're thinking):
I've just been reading a useful paper by Andrew Millard, which reviews the chronometric dates of African and Near Eastern fossil hominids from the Middle and early Late Pleistocene. The overall theme is that we don't know the dates nearly as well as we would like -- or as well as many comparative analyses have assumed.

This is always a useful sort of review. I swear there was a similar study done with North American C14 dates, but I'm having trouble finding the reference. My memory tickle is that someone applied the same strict criteria that have been used to judge pre-Clovis sites and found that a lot of accepted dates would be discarded as well. I'll post an update when/if I find it.

Obviously, people are going to look closer at unexpected or incongruous dates a lot harder than those that fit an accepted pattern; the whole "extraordinary claims require extraordinary proof" idea.

Hawks also highlights the cascade effect (quoting the paper):
In conducting this review of the chronometric evidence for African and Near Eastern hominids, the search for the detailed chronometric data was hampered by overreliance of many authors on the secondary literature. It is not uncommon to find a date cited from a publication, which upon checking simply cites another publication, which cites another, which cites the paper that first suggested the date. Frequently in such a chain of citations, the justification for the original date is lost, and in some cases, error limits disappear.

SJ Gould used to harp on this a lot, mostly in textbooks that propagated some scientific myth or other. He had a name for it that escapes me at the moment.

Grayson and Meltzer did a similar thing with Clovis hunting sites. As Hawks notes, everyone should probably be more careful when reviewing and citing others' work. OTOH, all you have to do is get some disagreement and someone is bound to go after the other side's assumptions with academic gusto.

UPDATE: Regarding the paper I'm trying to remember, there was the one last year by Waters and Stafford that did new AMS dates, but I'm thinking of something else.