Re: An alternative to ST and AAT

Gerrit Hanenburg (
Fri, 22 Nov 1996 11:53:39 GMT

"John Waters" <> wrote:

>In this context, an average life span of 22 years for A.
>africanus implies that the females must have given birth to
>their first infant at the age of eleven. This is similar to
>modern Chimpanzees. Interesting isn't it?

The regression equation for primates that relates female bodyweight to
age at first breeding for females,

log (age at first breeding)=log (43.5)+0.44*log (female bodyweight)
(age first breeding in days,bodyweight in grams) r=0.92

generates an age at first breeding for A.afarensis of 11.0 years.

What's even more interesting is that the age at death of several
juvenile hominids has been assessed on the basis of incremental growth
lines (striae of Retzius,a kind of dental equivalent of tree rings) in
their teeth. For Australopithecines this age was 3.15-3.48 years
(Bromage & Dean 1985). Some of these individuals died near the time of
eruption of the lower permanent M1 (SK 63,STS 24 and LH2)(Smith 1991).
Chimpanzees are known to erupt their lower permanent M1 at the age of
~3 years,while modern humans erupt theirs at ~6 years (Smith et al.
1994). This is also a strong indication that early hominids had an
ape-like developmental pattern.

Bromage,T.G.and Dean,M.C.(1985). Re-evaluation of the age at death of
immature fossil hominids. Nature 317:525-527.

Smith,B.H.(1991). Dental development and the evolution of life history
in Hominidae. Am.J.Phys.Anth.86:157-174.

Smith,B.H.,Crummet,T.L.and Brandt,K.L.(1994). Ages of eruption of
primate teeth:a compendium for aging individuals and comparing life
histories. Yearbook of Phys.Anth.37:177-231.