A new PNAS study has attempted to integrate the findings of lab research into fast evolution with the teachings of paleontology – which led the team of three biologists to distinguish between microevolution and macroevolution.
Microevolution can happen at timescales of 10-100 years, depending of course largely on the length of respective species’ generations. These should however be regarded as fluctuations that only rarely contribute to the large trends of evolution: macroevolution.
Such macroevolution evolution is large-scale, meaning it can lead to new species or for instance a significant increase or decrease in species’ body sizes. It takes places at an interval of ‘between 1 and 360’ million years, the researchers write.
Lead author Josef Uyeda of Oregon State University seems to support the punctuated equilibrium theory, as he mentions ‘stases’: periods of millions of years in which nothing much seems to be happening – something supported by the fossil record, but not by lab studies into genetic mutations. The stases are separated by ‘bursts of faster evolution’.
According to this theory ecology can actually hinder evolution through the very means that Darwin thought drove it: natural selection. This process seems to favour strengthening existing species, rather than creating niches for new ones to develop in. Only after a large ecological disturbance* is there sufficient space for biodiversity breakthroughs.
[In the end, for an ecosystems-managing species like ourselves, it would be down to setting the right priorities: ecology, or evolution? The Holocene Mass Extinction may indeed present Earth [already in the second half of her astronomically allowed lifetime] another nice chance for evolution, if you’d give that up to a million years. And evolution is good because it leads to biodiversity, life in numbers, sizes, volume and quality – even something as weirdly capable of doing stuff as us [slim chance that will evolve a second time]. But for biodiversity mass extinctions are of course always, by definition, more bad than good. So in the end perhaps trying to settle in our own multimillion year stasis would be the wisest thing to do? Unfortunately and unlike all stable species in Earth’s history before us, for humans reaching stasis requires a little more work than just sitting down.]
© Rolf Schuttenhelm | www.bitsofscience.org