What they say. . .

In the early 1990s, scientists began to discover that all life forms come from a startlingly limited number of genes. Humans, for example, have only twenty-five thousand genes, and we share sixty percent of them with bananas. How is it possible that we have so much in common genetically with a yellow fruit? A relatively new field called evolutionary developmental biology, or “evo-devo,” is tackling this question (among many others) by exploring the relationship between an organism’s development from embryo to adulthood and that organism’s genes. It has been discovered, for example, that seemingly random sequences of DNA, also known as “junk DNA,” act as “molecular fingers” that switch nearby genes on and off during development. Thus, part of how nature produces “endless forms most beautiful,” to use Darwin’s poetic phrasing, appears to be through the infinite combinations and patterns created when different genes are turned on or off at different times.

There is also growing evidence that organisms can switch their genes on or off in response to their environment, and that the memory of this gene activity can be passed on to subsequent generations. This happens through what’s called “epigenetics”—the nongenetic transfer of information through cells—and is only one of many systems of heredity that progressive scientists are now discovering influence evolution. So far, two other systems of heredity have been proposed in addition to the genetic and epigenetic: behavioral and symbolic (language).

What it means. . .

The work of these forward-thinking scientists is showing that natural selection acting upon random mutations of DNA is only a small part of the scientific story when it comes to explaining evolution. The incredible biodiversity of life is the product of a more complex, elegant, and subtle interplay between genes, cells, parents, offspring, and the environment than perhaps anyone imagined. One result of these discoveries is that we now know that systems of heredity themselves are evolving, and some profound questions once off limits to “serious” scientists (for instance, Can organisms direct their own evolution?) are now becoming unavoidable.

“There is a new sense of humility. . . . The discoveries being made show how enormously complicated everything is. . . . The popular conception of the gene as a simple causal agent is not valid.”

Eva Jablonka and Marion Lamb