There is considerable argument about whether the
Dikika girl could also climb trees like an ape.
This climbing ability would require anatomical
equipment like long arms, and the 'Lucy' species had arms that
dangled down to just above the knees. It also had gorilla-like
shoulder blades which suggest it could have been skilled at
swinging through trees.
But the question is whether such features
indicate climbing ability or are just 'evolutionary baggage'.
The Dikika girl had an estimated brain size
of 330 cubic centimetres when she died, which is not very different
from that of a similarly aged chimpanzee. However, when compared
to the adult afarensis values, it forms between 63-88% of
the adult brain size.
This is lower than that of an adult chimp, where
by the age of three, over 90% of the brain is formed. This relatively
slow brain growth in the Dikika girl appears to be slightly closer
to that of humans.
Slow, gradual development in an extended childhood
is regarded as a very human trait - probably to enable our higher
functions to develop.
Professor Fred Spoor of University College London
said the find would give scientists a 'detailed insight into how
our distant relatives grew up and behaved... at a time in human
evolution at which they looked a good deal more like bipedal
chimpanzees than like us'.
Dr Jonathan Wynn of the University of St Andrews in
the UK and colleagues at the University of South Florida dated the
sediments surrounding the remains and came up with an age of 3.3
The 'Lucy' skeleton, discovered in Hadar, Ethiopia,
in 1974 belongs to the same species as the Dikika girl. For more
than twenty years it was the oldest human ancestor known to science.