Friday, August 04, 2006
Organisms, including humans, all inherit DNA from generation to generation, what biologists call hard inheritance, because the nucleotide sequence of DNA is constant and only changes by rare random mutation as it is passed down the generations.
But there also is evidence, especially in plants, that non-genetic factors modifying the DNA can also be inherited. The modifications of the genetic material take the form of small chemical additions to one of the DNA bases and the alternative packaging of the DNA. These so-called epigenetic modifications are known to be important for turning genes on and off during the course of an organism's life, but their importance in controlling inheritance has been debated. Many biologists are skeptical of any form of soft inheritance, where the genetic material is not constant, believing that it is only genetic information - DNA -- that can be passed onto generations.
Now Eric Richards, Ph.D., professor of biology at Washington University in St. Louis, writing in the May issue of Nature Reviews Genetics (Abstract), analyzes recent and past research in epigenetics and the history of evolution and proposes that epigenetics should be considered a form of soft inheritance, citing examples in both the plant and mammalian kingdoms.
In doing so, he evokes the pre-Darwinian evolutionist Jean-Baptiste Lamarck (1744-1829), a name that evolutionary biologists thought long ago left the stage, and Soviet agronomist T.D. Lysenko. Lamarck, and more recent neo-Lamarckian researchers, believed that the environment plays a key role in a species acquiring inherited characteristics that drive variation and evolution.
See an online edition of Lamarck's Zoological Philosophy
Richards' paper also appears in the Wanted Papers category.