Lake Victoria, Africa's largest lake, is home to more than 300 species of
cichlids. These fish, which are popular in aquariums, are deep-bodied and
have one nostril, rather than the usual two, on each side of the head.
So what, you say? Well, what's surprising is that Lake Victoria was bone
dry not very long ago, suggesting that all the cichlids in it have
evolved in a remarkably short time. Seismic profiles and cores of the
lake taken by a team headed by Thomas C. Johnson of the University of
Minnesota, reveal that the lake dried up completely about 12,400 years
ago. This means that the rate of speciation of cichlid fishes has been
extremely rapid: something on average of one new species every 40 years!
All this progress has some people thinking, particularly anomaly hunter
and The Sourcebook
Project compiler William Corliss. In his newsletter, Science
Frontiers, Corliss asks the question on everybody's mind: "Can
random mutations -- the accepted source of evolutionary novelty -- have
generated so many new species in such a short time?" We decided to pose that
question to Boston University biologist Les Kaufman, who does research on these
fish in the Lake Victoria region.
"My work suggests that the actual duration of the burst that produced the
current fauna was much shorter than even the 12,400 years that the lake
has been recently full of water," Kaufman says. "It is likely that many
of the species formed during the refilling of the lake. However, they
appear to be derived from a diversity of lineages that evolved during
previous episodes during which there was a large lake in the basin.
"By the way," Kaufman adds, "as remarkable as the timing may sound, there
is nothing in it that is inconsistent with existing evolutionary theory. It is
just jarring to be reminded that evolution is real and happens quickly."
Fresh fish, indeed.
--Patrick Huyghe
We smell fish, lots of fish.