Travel Reference
In-Depth Information
Species like the burrowing
Spalax
, which do not migrate long distances,
might be easily split if barriers are put in their way. Already, a new road that
runs through part of the canyon is introducing stronger barriers to the free
exchange of genes. Mole rats cannot burrow under the road, because they
depend on oxygen that dif uses from the surface. The road's impermeable tar-
mac prevents this dif usion. Other, above-ground species may not be able to
move quickly enough to dodge Israeli drivers. Of such small changes is most
evolution made.
Nevo's work in Evolution Canyon, along with similarly detailed evolu-
tionary scenarios that have been uncovered by thousands of other scientists
in every part of the world, have given us profound insights into how evolu-
tion happens. This new work goes far beyond the early insights of Darwin,
who knew nothing of genes or gene pools. We now know that evolution is
a dynamic process in which changes in the composition of gene pools are
driven by natural selection. Severe environments increase the ef ectiveness
of natural selection. They may also introduce more mutations, the ultimate
raw material of evolution.
Nevo has spent his life studying how changes in the genetic structure of
populations can be linked to ecological dif erences. At the end of our visit
to the canyon he encouraged our little group of scientists and students to
collaborate in his ongoing studies. His twinkling enthusiasm has inspired
generations of students from around the world to come to Evolution Canyon
so that they can fi nd out how evolution really happens.
Eats shoots and leaves
The study of how genes have evolved has revealed a profound truth about
how evolution works. Evolution rarely starts from scratch. Instead it utilizes
genes and genetic pathways that have already been shaped by natural selec-
tion to solve a dif erent adaptive problem.
Evolution boils down to a matter of probabilities. It is quite likely, for
example, that an extra copy of a gene will be inserted into a genome by muta-
tion. Once the new copy of the gene has appeared, it can evolve to take up a
