Geoscience Reference
In-Depth Information
Figure 16.1. Molar of Pliocene
Elephas recki
used to build stone enclosure for baby
goats, Afar Desert, Ethiopia.
sites (Jousse,
2004
) or with former lakes (Wendorf et al.,
1993
; Gautier et al.,
1994
;
Ve r n e t ,
1995
; Tillet,
1997
). Fossil bones found in river sediments have generally been
reworked and suffer from the results of differential transport and differential preser-
vation. In the case of smaller mammals, the bones are often broken up and highly
weathered, making them difficult to date. Exceptions to the general rarity of vertebrate
fossil remains in deserts are the East African and Afar rifts, which have yielded an
abundance of well-preserved bones and teeth (Vrba et al.,
1995
; de Heinzelin et al.,
2000
)(
Figures 16.1
and
16.2
), and the limestone caves of semi-arid southern Africa
(Brain,
1981b
) and of semi-arid South Australia (Macken et al.,
2012
). In all of
these cases, caution is needed when seeking to infer past habitats from the fossil
remains, because the remains will reflect location at the time of death, together with
any disturbance from scavenging carnivores and vultures, followed by the possible
effects of mass movement and run-off. An entire branch of vertebrate palaeontology,
taphonomy, is devoted to unravelling these effects. Given that the rate of speciation of
large vertebrates is relatively slow (amounting to about 0.5 Ma for large bovids), an
independent means of dating the fossil assemblage is essential if they are to provide
useful information about past ecosystems and climates. One vertebrate that has been
the focus of unparalleled study is the hominid family, which includes both modern
humans (
Homo sapiens
) and our prehistoric ancestors, the
Australopithecines
, detailed
in the next chapter (
Chapter 17
).
