Elaine Morgan (
Sun, 06 Aug 1995 12:01:40 GMT

Let's deal with the first section on Duncan's List: the kind of habitat
A afarensis lived in (Anatomy will follow later)

In my scenario, they were in the post-aquatic phase. They were on the
mainland, had found fresh water, were spreading upstream along the
chain of Rift Valley waterways. I imagine them finding and frequenting
lakes and rivers fringed with gallery forest, with
stretches of marshes and deltas and floodplains

In your scenario they have until recently never left the trees. They
are only doing it now because open spaces are beginning to appear in
the forest. You imagine them frequenting these spaces for at least
part of the time; it is these forays, however brief or
intermittent, which are causing the trend to bipedalism. If I have
misrepresented the s/ mosaic scenario here, please let me know.

In your recommended texts, the two sites described in the greatest
detail were Hadar and Laetoli. Broadly speaking, Hadar best fits my
scenario and Laetoli best fits yours.

The keynote phrases in the descriptions of the Hadar site through the
ages are : "Three elements: distal braided rivers, a major meandering
river, and a lake with possibly swampy borders" ...."a floodplain and a
marsh" ..." a freshwater lake" "a paleolake" ..."lacustrine
conditions" ..."ostracod beds".."the environment definitely a swamp or
a shallow lake"..."local marshes would have been intensively developed"
The paleolake varied in size, swelling and shrinking. Nearby there was
bush and forested vegetation. At some periods the pollen deposits
prove that the landscape grew drier, with some grass. That did not mean
the lake disappeared, because the pollen proving there was grass was
recovered from "lacustrine sediments" i.e. it was blown into the water.
And Lucy did not die on the grass. She died in sand at the water's
edge, as you know, among crocodiles turtles and crabs.

For savannah theorists Laetoli was the jewel in the crown. It is where
the famous footprints were found, on a dry plain, at the very end of
the dry season, with all the grass and vegetation bitten down to the
ground. Vegetation like the Serengeti. It is (I believe - is this
correct?)the only place in the Rift Valley where traces of hominids
have been found in air-borne rather than water-borne sediments.

A book about Laetoli by Leakey and Harris was in preparation when
savannah theory still ruled. By the time it was published it was
already a tiny bit embarrassing in its stress on aridity. P.J.Andrews
"..evidence is that the habitat was more heavily wooded than any of the
authors are prepared to acknowledge. If there is any one criticism
I woud make of this book it is the uncritical acceptance of unspecified
savannah habitat. at Laetoli".

But that was okay, because it certainly fitted the revised version:
savvanh mosaic. There was grass pollen, traces of grass roots, the
fossils of grassland herbivores. And the hominids who left the
footprints were far from any lake or river. So the score is one all.

The question remains: which of these two environments was more typical
of the habitat favoured by afarensis? As far as the fossil evidence
goes, Laetoli is the odd one out. All the other afarensis sites are
near water. It is argued that the sample is untypical because only the
lacustrine and fluviatile and paludrine skeletons would have been
preserved. Nevertheless apart from Laetoli they are the only evidence
we have. Apart from Laetoli, the water's edge specimens are hard
evidence, the s/mosaic ones are speculation.

If I claim Laetoli is the odd one out, the onus is on me to account for
the presence of afaransis there, on an arid plain, so far from their
accustomed stamping-grounds.

Afarensis is not the only species whose presence there needs accounting
for. There seems to be a distinct discrepancy between the evidence of
the flora and the evidence of the fauna. The fossil pollen shows
"vegetation little different from the savannah grassland present
today". In fact grass-pollen proportions were even higher then than

But the animals do not match that picture. There were for example four
species of cercopithecoids, a range of primate diversity normally only
found in tropical forests. Among the rodents, species diversity is "too
high for a single community from a savannah habitat". There's a galago,
who belongs in the forest canopy - what's he doing there? Carnivore
groups show "extremely high species diversity." There are three
different species of giraffids, all described as browsers normally
requiring woodland habitats". All this on the plain at the fag end of
the dry season, The shower of rain that preserved the footprints is
held to have been the first rain for months. Why were they all there?

Numbers of them left their footprints in the same tuff as the hominids.
We are told that "many of them" (which I take to mean less than a
majority" were proceeding calmly at a walking pace. What were the
others doing - running? Formerly the hominids were described as
strolling, because the prints are not very far apart. But Susman says,
because of their anatomy, that stride was as long as they could
achieve. And perhaps they were tired. We don't know how far they;d come.

The volcano Sadiman, 30 km to the east, was very active at that time.
There were repeated falls of the kind of lava ash which fell on the
prints and preserved them - ten in all, over "a very short time".
Species diversity is even higher in the upper layers than in the lower
ones - more and more animals coming in from elsewhere. All the evidence
suggests a frightening episode of successive volcanic eruptions. It is
possible that the sunbaked vegetation in the vicinity of Sadiman within
reach of the lava flow caught fire. I believe an appreciable percentage
of the "mixed assemblage" which so puzzled Andrews consisted not of
residents but of transients milling around trying to find a way of
escaping the fire on the horizon and the choking ash, and the bipeds
may well have been among the refugees.