Evoluzione - Appunti sull'evoluzionismo
Appunti sulle tappe principali che hanno portato alla teoria dell’evoluzione di Charles Darwin
Amplify’d from www.traccedistudio.it
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Salvaging Lamarck
While many credit Darwin as the father of evolution, there were many before him who began to think about ways in which both the human and non-human physiology may have adapted over time. Probably the first to come up with a working theory for this was French naturalist Jean-Baptiste Lamarck. Although Lamarck had correctly identified an evolutionary connection in species, the mechanism which he proposed seemed to be faulty. According to Lamarck, species underwent adaptations during their lifespans that were then passed onto their progeny. Testing this theory, German biologist August Weismann conducted an experiment where he chopped off the tails of some 1500 rats over 20 generations. Weismann noted that not one rat from the experiment was born without a tail. At the same time, Darwin’s theory of Natural Selection gained traction, and it seemed that Lamarck’s theory was put to rest for good.
Fast forward nearly 150 years and enter the burgeoning science of Epigenetics. Researchers are now finding that instances in which the environment of our forebears does in fact alter our DNA. Scientists are now beginning to believe that environmental effects can indeed change inherited traits, strikingly similar to the theory that Lamarck had advanced.
“Lamarck also recognized that species were adapted to their environment. He explained this observation by saying that the same nervous fluid driving increasing complexity, also caused the organs of an animal (or a plant) to change based on the use or disuse of that organ, just as muscles are affected by exercise. He argued that these changes would be inherited by the next generation and produce slow adaptation to the environment.”
—I’m pretty sure this is it. Giraffes started out as a “simple” species with “regular” necks but found they couldn’t reach the trees, so after years of stretching to try and reach the leaves, their necks elongated to the point where it was so environmentally favourable that giraffes were eventually just born with long necks.Words and History
I watch a show called Once upon a Time, and the most recent episode (4/1/12, “The Stable Boy”) had an interesting way of approaching a problem. An author character was talking to the sheriff, and suggested that she get past her block on an investigation the same way he gets past writer’s block: Reread, now knowing how the story so far goes.
This is great for moving forward, I think, because we already know how we saw the story at that point in time. But, it works because it adds a perspective. There is something important about this perspective. There is also something important in how the author saw it the first time through.
History is a study in retrospect. We work like the author rereading a work to see where it was, in relation to the moment of where it is. The problem is, we don’t always remember to think back on what is was when it was.
So do you guys remember learning about Lamarck in high school biology class when studying evolution? He’s the giraffe guy. You know, had the theory that giraffe necks got longer over time because they wanted to reach leaves and they gained that from their parents and grandparents and so on. We always laughed at him him and said how stupid he was, saying “Darwin knows what is up and Lamarck is just plain dumb”. Though Darwin was incredibly intelligent beyond belief, there is no reason to shoot down Lamarck because of his theory. It was not correct but it wasn’t totally out there! I would have probably thought the same thing in that day and age too. But anyway, that is not what this post is about exactly. After reading a lot on epigenetics and how what we eat and what we are exposed to becomes “memorized” in our genome (epigenome more specifically), it gets passed on to our offspring, so that must contribute to evolution, right? Lamarck’s theory was that acquired characteristics can become inherited. Though the idea of stretching your neck all day would make your offspring have long necks is wrong, the idea that changes to your epigenome can get passed on is true! (Though remember that epigenetics is not just about inheritance. Most of it involves changes of expression during development. The exact definition of epigenetics is always being debated as well) And changes to your epigenome can occur from eating that hot dog or smoking that cigarette. I mean, we haven’t investigated epigenetics in evolution that much, so this is basically unknown in terms of long periods but when gene expression levels change, the individual produces different amounts and levels of proteins and that changes what the body can do. Maybe Lamarck was onto something (obviously not this specific; genetics was completely unheard of at the time. Even Darwin did not know of it but knew the idea of it).
Anyway, I just thought this was cool and wanted to share. I’m personally more interested in epigenetic mechanisms and their influence on diseases and during early development but I do love evolution and immensely enjoyed the class I took on it last fall. Understanding epigenetic changes over time could be something really interesting to look into. It may be 200 years late, but damn Lamarck, you had the right idea!
