From DAVID D. SCARBORO
The article ‘The case against Eve’ in the issue of 22 June leans towards
the view that modern humans evolved in several places simultaneously. I
have difficulty on theoretical grounds in understanding how this could have
happened.
Reproductive isolation creates the conditions in which speciation can
take place by the divergence of isolated populations from the parent species.
How, then, could isolated populations of Homo erectus simultaneously evolve
in parallel without diverging, producing widely scattered populations which
fulfil the criteria that define membership of a single species? The theory
that modern humans evolved in Africa from a single population of Homo erectus
and spread out from there accords better with current evolutionary theory,
regardless of whether their radiation involved conquest or mixing with the
locals. If reproductive isolation leads to speciation in butterflies and
brachiopods, why should humans be any different?
David D. Scarboro Reading, Berkshire
