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Further research established that the inherited change had altered the chicks' "gene expression" – the way certain genes are turned "on" or
"off", bestowing any given animal with specific traits. The stress had affected the mother hens on a genetic level, and they had passed it on to
their offspring.
The Swedish chicken study was one of several recent breakthroughs in the youthful field of epigenetics, which primarily studies the epigenome, the
protective package of proteins around which genetic material – strands of DNA – is wrapped. The epigenome plays a crucial role in determining
which genes actually express themselves in a creature's traits: in effect, it switches certain genes on or off, or turns them up or down in
intensity. It isn't news that the environment can alter the epigenome; what's news is that those changes can be inherited. And this doesn't, of
course, apply only to chickens: some of the most striking findings come from research involving humans.
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We've learned that huge proportions of the human genome consist of viruses, or virus-like materials, raising the notion that they got there through
infection – meaning that natural selection acts not just on random mutations, but on new stuff that's introduced from elsewhere. Relatedly, there
is growing evidence, at the level of microbes, of genes being transferred not just vertically, from ancestors to parents to offspring, but also
horizontally, between organisms.
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For instance, fruit flies exposed to a drug called geldanamycin show unusual outgrowths on their eyes that can last through at least 13 generations of
offspring even though no change in DNA has occurred (and generations 2 through 13 were not directly exposed to the drug). Similarly, according to a
paper published last year in the Quarterly Review of Biology by Eva Jablonka (an epigenetic pioneer) and Gal Raz of Tel Aviv University, roundworms
fed with a kind of bacteria can feature a small, dumpy appearance and a switched-off green fluorescent protein; the changes last at least 40
generations. (Jablonka and Raz's paper catalogs some 100 forms of epigenetic inheritance.)
Darwin, who was 84 years younger than Lamarck, was the better scientist, and he won the day. Lamarckian evolution came to be seen as a scientific
blunder. Yet epigenetics is now forcing scientists to re-evaluate Lamarck's ideas.
The coherence between the ALSPAC and Overkalix results in terms of the exposure-sensitive periods and sex specificity supports the hypothesis that
there is a general mechanism for transmitting information about the ancestral environment down the male line," Pembrey, Bygren, Golding and their
colleagues concluded in the European Journal of Human Genetics paper. In other words, you can change your epigenetics even when you make a dumb
decision at 10 years old. If you start smoking then, you may have made not only a medical mistake but a catastrophic genetic mistake.
There are at least 210 cell types in the human body — and possibly far more, according to Ecker, the Salk biologist, who worked on the epigenome
maps. Each of the 210 cell types is likely to have a different epigenome.
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Now, with advantageous genetic innovations able to flow horizontally across the entire system the code readily discovered the overall optimal
structure and came to be universal among all organisms. "In some sense," says Woese, "the genetic code is a fossil or perhaps an echo of the origin
of life, just as the cosmic microwave background is a sort of echo of the big bang. And its form points to a process very different from today's
Darwinian evolution." For the researchers the conclusion is inescapable: the genetic code must have arisen in an earlier evolutionary phase dominated
by horizontal gene transfer.
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As more genomes are sequenced, ever more incongruous sequences of DNA are turning up. Comparisons of the genomes of various species including a frog,
lizard, mouse and bushbaby, for example, indicate that one particular chunk of DNA found in each must have been acquired independently by horizontal
gene transfer (Proceedings of the National Academy of Sciences, vol 105, p 17023). "The importance of this for evolution has yet to be seriously
considered."