In today’s Daily (pseudo)Science Update, Yeast Adapt, But Don’t Evolve, we have a discussion of a study on the capacity for yeast to Evolve/Adapt to environmental changes. Why Mr Thomas links to the Science article that we can only see part of, rather than the Time blog postwe can read completely I don’t know. The study “tracked the fate of over 2,000 populations of yeast over a period of several months”, testing their ability to evolve in the face of changes in salt concentration in their environment. Their results were surprising – yeast seems to be able to adapt in only around “50 – 100 generations”.
As Mr Thomas himself says:
If evolution works the way that neo-Darwinism has proposed, then accidental mutations in some yeast individuals should lead to new molecules that help the organism cope with a saltier environment—as long as the environment doesn’t change too fast for the mutations to keep pace.
As this is exactly what the study found, and is a pretty decent summary of the whole thing, the DpSU is largely concerned about why this is apparently not a massive tour-de-force for “neo-Darwinism” (or evolution for those of us that don’t think they need to lump it in with all the other ‘ism’s in an attempt to be derogatory) and is instead a product of “adaptation”.
First, however, we must have a long and rather vague non-description of how salt is regulated in the cell, in such a way as to imply design, without overtly stating it. (“elegant and miniaturized system”, “ingenious machines” etc – I talked here about how, as natural selection and human engineering goes about ‘designing’ systems is very different, comparing the two even by using the same terminology can be disingenuous).
He then makes the completely and utterly unreferenced or otherwise backed up claim that:
Yeast adapted too fast to fit the idea that random mutations are responsible, since mutations accumulate very slowly. This quickness to adapt therefore argues in favor of the idea that yeast were already equipped with adaptive systems.
Exactly what these “adaptive systems” are, he doesn’t elaborate. To be charitable, I might say that he means that some yeasts already had that ability to survive the salt changes – that is the gene or whatever for it already existed in the population – and the changes merely selected strongly in favour of individuals that did so, making that trait the dominant one in the gene pool. However, this is directly contrary to the conclusions of the study itself – they, at least, are quite definitely talking about “adapt[ation] through the accumulation of beneficial mutations”. Secondly, if the capacity for survival was already there, and did not require any “random mutations”, it should have been even faster – less than a dozen mutations I would think, rather than the “50 – 100” found. And weren’t we just talking about how mutations happen too fast to be good?
Anyway, I don’t think he was talking about that. He seems to be implying that there is some, almost Lamarkian mechanism of adaptation inherent in Yeast (and, presumably, other things). As he claims, “they were specially created with an ability to rapidly adapt to, and survive in, a variety of conditions”.
Secondly, we have this:
Further, an insistence that these yeast adapted this efficiently by means of mutations invites other conundrums. If these observed adaptations are called “evolution,” and if they happen in as few as 50 to 100 generations, then why have yeast not continued to evolve and become totally different creatures by now?
With their accelerated “evolutionary” pace of adaptation, why have they been evolutionarily stagnant for uncounted trillions of generations? Since the earliest recorded times, mankind has been using the same yeast to make bread and beer, and in the last half-century, scientists have been studying yeast in laboratories ad infinitum. Yet none of the organisms has evolved beyond yeast.
Let’s see… First, we need to remind ourselves how evolution occurs. Natural selection causes a change in frequency of genetic traits. This is caused by the relative fitness of the organisms that exhibit them. Over time, ceteris paribus as the economists say, the organisms home in on the vicinity an equilibrium, which is that situations best combination of traits. If all organisms are at the equilibrium, save one that is not, that one will be selected against. This negative feedback cycle is what keeps species largely constant over time. This point of equilibrium can only change if the environment changes. Unless scientists are doing evolution related experiments on the yeast, they are unlikely to be putting the yeast into a non-ideal environment (and with regards to baking, allowing yeast to reproduce massively in an over-ideal environment and then killing the lot of them is not very conducive to evolution). This means that it is not likely that yeast would evolve under their noses – there’s not need for it to.
And what is a “species” exactly anyway? It’s a pretty arbitrary term, at least when applied temporally. You can’t easily define when one species evolves into another. And what is ‘yeast’? While in this case we are referring to a specific species, Saccharomyces cerevisiae, the common baker’s yeast, ‘yeast’ is a pretty amorphous term anyway. The best definition seems to be ‘unicellular fungus’, but even that isn’t perfect, as we shall see shortly. This is not an easy definition to evolve out of…
Another thing to nit-pick about before I leave this article behind forever. If the “trillions of generations” are uncounted, how do we know that yeast has been stagnant for all that time? And I can only presume that ‘trillions’ is an exaggeration. Assuming a generation time of a singe second, a trillion generations comes out at more than thirty one thousand years, far longer than these Ussher-following YECs think the world has existed.
On the day after the source of this DpSU came out (that is, on the 23rd of June), in the New Scientist there was an article on yeast evolution also. In this case, yeast was persuaded to make the leap to simple multicellularity. This, arguably, consists of an answer to Mr Thomas’ claim above. Admittedly, as the New Scientist article says, the experiment is not a perfect demonstration of the evolution of multicellularity. Is is believed that the yeast’s ancestors – more than 10 million years ago, mind. Well out of the time range of Young Earth Creationists – were once multicellular, meaning that the capacity might still have been there. So, the experimenters want to test on other things not known to have been multicellular. While Science marches on, Creationists sit in the dust and play.