Sex on Six Legs_ Lessons on Life, Love, and Language From the Insect World - Marlene Zuk [20]
Before explaining sociogenomics, a bit of background about the new age of genomics, and about what we mean by sequencing a genome or having a "genome project," is in order. The genome is the total set of DNA in an organism, arranged into the chromosomes that are characteristic of each species; humans have twenty-three pairs of chromosomes, while cats have nineteen pairs, cows have thirty, silkworms have twenty-seven or twenty-eight, and a species of ant has just one. Sequencing a genome means determining the order of the four chemical bases that are the building blocks of the helix of DNA. The bases are called adenine, thymine, guanine, and cytosine, usually abbreviated with their initials A, T, G, and C. The genes themselves are particular sequences of the bases that contain instructions on the manufacture of proteins that make up the structure of the body or instructions on regulating when and how other genes become activated. Not all of the DNA consists of genes; scientists knew going into the Human Genome Project, the first of such efforts, that some amount of the material on the chromosomes would be noncoding, meaning it does not contain information about either gene regulation or the making of a protein. The genome sequence therefore consists of a long—a very, very long—string of four letters, grouped together in a particular arrangement unique to each species.
Once the Human Genome Project was completed in 2003, it was clear that more genomes needed sequencing. Many scientists wanted to put two animals next on the list. First would be the zebra fish, as a way to examine genes responsible for the development of a fertilized egg into an adult organism, and then the laboratory mouse, because as a mammal we could more easily compare its genes to those of people. Nobel laureate Sydney Brenner demurred, saying that "the mouse is too close. It hasn't had enough time to randomize, so you are confused by the commonness of origin."
What he means is that because we so recently shared a common ancestor with mice, our genetic material is already very similar to theirs. But which genes are the essential ones, the ones retained through hundreds of millions of years? How have genes changed to perform different functions? To answer that, we need insects. It's been 250 million years since the mosquito Anopheles gambiae and the fruit fly Drosophila melanogaster shared a common ancestor. That's roughly the same evolutionary distance that exists between humans and fishes, a third more than the distance between humans and chickens.
Of course, it's not an either-or situation. The zebra fish and mouse genomes have now been sequenced, along with those of the chicken, the African clawed frog, and a nematode called Caenorhabditis elegans. Genome projects are in progress for a whole host of others, including the European hedgehog, the green anole (a small lizard often sold in pet stores as a chameleon, although it is only distantly related to the true chameleons), and the gorilla, in addition to many invertebrates. Nevertheless, insects can reveal the process of evolution in ways that no other group of organisms can.
As I already pointed out, insects are the most diverse group of organisms on the planet—there are more kinds of insects than any other organism, they live