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If the history of life on Earth can teach us anything, it is this: as conditions change, species either adapt or become extinct. In our time of considerable environmental change, humanity should consider its options. No species, even the almighty Homo sapiens, can stop evolution completely. But we can choose to limit our capacity for ongoing biological adaptation in an effort to remain ever the same by keeping populations isolated. Of course, such decisions are not made by humanity as a whole but by individuals and governments. Nationalism and xenophobia, on the rise in the US and Europe, threaten to decrease genetic exchange between populations, stifling our ability to continue evolving and adapting.Alternatively, we can embrace immigration and globalisation in an effort to position ourselves for a brighter future.

Those findings apply to a single generation, yet they tug at the edges of evolutionary theory, in which species change slowly over millennia, not rapidly over the months or years of a single life. Charles Darwin’s process of natural selection holds that nature choses the best-adapted organisms to reproduce and survive in any given ecosystem. The process operates when DNA sequences mutate randomly, and organisms with the specific sequences best-adapted to the environment multiply and prevail – causing gene expression to shift. Yet as surely as the slow march of Darwinian evolution shapes life on Earth over aeons, scientists have found that epigenetic signals can work each day, and not just through methyl groups. Experience in the environment could also alter chromatin, the molecular matrix making up our chromosomes; RNA, the messenger molecules that translate genetic instructions from DNA into protein; and histones, the proteins involved in packaging and structuring the chromatin comprising the genes.