On Hox Genes
In the 1980s, researchers discovered a series of genes
called Hox genes that set the identity
of segments of insect bodies from head to tail. Mutations
to Hox genes can put an entire leg where an antenna should sprout out (right) and produce other equally grotesque
Interestingly, insects and humans also inherited Hox genes. In us, these genes control
the development of our head-to-tail anatomy
as embryos. Similar genes controlling the eyes of insects and our own eyes have also been discovered. (Our version
of the gene can be inserted in a fly and still trigger the building of an insect eye!) It now appears that some
600 million years ago, a common ancestor of most animals on Earth today acquired a "genetic toolkit"
of these body-building genes. Although the structures that these genes build have changed, the genes have been
conserved. It is a discovery that would have delighted Darwin and astonished him greatly.