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Observing Evolution Over 40,000 Generations
Last year we discussed the work of Richard Lenski, who has been breeding E. coli for 21 years in a laboratory in Michigan. Then, the news was that Lenski's lab had caught direct, reproducible evidence of a genetic mutation with functional consequences for an organism. Now Lenski's lab has published in Nature a major study comparing adaptive and random genetic changes in 40,000 generations of E. coli (abstract here). "Early changes in the bacteria appeared to be largely adaptive, helping them be more successful in their environment. 'The genome was evolving along at a surprisingly constant rate, even as the adaptation of the bacteria slowed down,' [Lenski] noted. 'But then suddenly the mutation rate jumped way up, and a new dynamic relationship was established.' By generation 20,000, for example, the group found that some 45 genetic mutations had occurred, but 6,000 generations later a genetic mutation in the metabolism arose and sparked a rapid increase in the number of mutations so that by generation 40,000, some 653 mutations had occurred. Unlike the earlier changes, many of these later mutations appeared to be more random and neutral. The long-awaited findings show that calculating rates and types of evolutionary change may be even more difficult to do without a rich data set."
god did it
Meant as a joke but it will sadly happen like this. It is incredible that we can have this level of clear investigation into evolution. And it is something that people have innately known since early agriculture (replanting grain using the best seeds, genetic engineering). Yet in the US:
51% of people believe god created man as he is.
30% said god created us and we can evolve
15% say humans evolved with out god.
These figures are a terrifying example of humans ability to deny what should be blatantly obvious. If we can do this imagine how many things people must get completely wrong no matter the level of obviousness.
These figures are incredible examples of how much money you can make on peoples stupidity.
I am the lawn!
ALL mutations are random. If they are advantageous, great, than it is likely that they will be passed along.
"Look, I believe in evolution, but never has there been found a parent species to something alive today. In other words, scientists can not point at any two distinct species, living or extinct, plant or animal, and say that this species evolved directly from that one."
Of course not. That's kind of like pointing to two leaves on a tree and saying one leaf came from the other. It doesn't work that way. They are both on the terminations of the branches, and the node where they branched into two is in the past. Ordinarily, the common ancestor is long dead. The nice thing with these E. coli is that the researchers kept a portion of the ancestral population intact, and the specimens are clones, so while not the actual ancestor of the lineage that kept going, they are genetically identical.
There are plenty of fossils that are close to branch points, and as more fossils are found there are still plenty of gaps left, as there always will be, but the changes necessary to span those gaps get smaller and smaller as the sampling improves. For example, Anchiornis was just discovered in the last couple of years, and a new specimen described a few weeks ago. Dinosaur? Bird? It's rather arbitrary to decide. It's either a wing-clawed, long-tailed, toothed bird like no modern bird, or it is a flight-feathered, gliding dinosaur. As if they were the leaves on a tree, birds and reptiles look distinct now, but follow the branches back far enough and they get mighty blurred together. This is hardly an isolated example.
There are fish that look so tetrapod-like that when the skull was initially found separately they thought it was a tetrapod. Then workers found the rest of the body and realized it was a fish. There are other tetrapod-like fish, such as Tiktaalik . But go back 100 years and these species weren't known at all.
I really don't know what more skeptics are expecting. Perfection? It won't happen. It's not like we'll ever have every twig on the tree. Good fossils are rare. But the statistical pattern with increased sampling is quite robust.
This is not entirely true, E. Coli is known to be able to metabolise glucose. The bacteria were "grown" in a solution that included glucose as it's main component. There were also many populations of the bacteria that were being evolved seperately (they NEVER mixed). Suddenly, in one population, a bacteria emerged that could metabolise citrate. This gave that bacteria a massive advantage, because it could now consume two types of food and it had no competition for the citrate (unlike glucose, which all the other bacteria could consume as well).
This also allowed the total population in that group to explode (there's now more food in total, glucose + citrate).
Another cool thing is that this smashes the "Irreducible Complexity" argument. The ability to metabolise citrate is developed by two separate mutations, which, on their own achieve nothing. Some of the populations developed the first mutation and some developed the second one, but none of them had previously developed both. This shows that the "preliminary" mutations were not harmful to the bacteria, so they just "hung around" until one of them was lucky enough to get the second mutation too.
Anyway, look up Lenski's work, I'm sure his papers (and those of his students/colleagues) are better at explaining it all than me...
1178161 is prime...