of the longest and most important work in this regard has followed the existence of 68,000 generations of Escherichia coli bacteria for nearly thirty years - the equivalent in human terms of a million years of evolutionary history.
YOU ARE NEVER "ARRIVED". Now some important research results started in 1988 (the Long-Term Evolution Experiment, which for the record is not finished at all and will not end soon) have been published on Nature.
The conclusions undermine one of the many common areas in the subject, namely the idea of "fitness peaks": it is not true for every given species there is a perfect number of mutations beyond which any new change would end up worsening things .
On the contrary, evolution continues to be imperfect: there are no organisms so well adapted to their habitats that they no longer need adjustments.
THE METHOD. In the Michigan State University study, 12 E. coli populations were monitored in independent microcosms, taking every 75 days (ie every 500 generations) a portion of the bacterial solution to be frozen as a "time capsule" of the genetic situation at that time .
IN DIVERSE. Genetic mutations were then mapped and reconstructed over time. In three decades, bacterial cells have become larger and E. coli have become more efficient in metabolizing glucose in their culture. Beyond the evolutionary achievements of one or the other population, the surprising thing is that mutations continue - albeit at a slower rate - even today, despite crop conditions being largely stable.
CHANGE CHANGES. One possible explanation is that the bacteria modify their habitat slightly, and then adapt to the changes induced by them. The study will serve to understand some evolutionary mechanisms that concern us closely. Some super bacteria are evolving antibiotic resistance, and the man itself causes changes in his habitat, which he is still adapting to.
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