The present-day faunas of the great African lakes present some of the world's best examples
of 'explosive speciation'. Lakes Victoria and Malawi each probably have several hundred
endemic species of cichlid fishes. Much can be inferred about the evolution of these fishes
from morphology, behaviour and intra-lacustrine distribution and from the fact that they
include taxa ranging from local races, through sibling species, to forms that display
extensive differentiation. The time taken to acquire specific distinctness can sometimes
be accurately defined, but fossil lineages are unknown. A recent study of a fossil sequence
of molluscs in the Turkana basin throws new light on the history of African lake faunas.
It also claims to have resolved events during speciation. While critical analysis based on
our knowledge of living molluscs in this area fails to substantiate this claim, the fossil
molluscs complement information provided by the biology of extant fishes and invertebrates
and emphasize the importance of these lakes in the study of evolution in living and extinct
populations.