It makes complete sense to me that when poachers are shooting elephants with the largest tusks that the ones left have smaller tusks, breed and pass on the smaller tusk genetics. I don't see how that is evolution in action. By that I mean that I still don't know anyone who denies that micro evolution within a species takes place. Every species changes especially when the breeding population is very localised. I mean look at the fact that Swedes look very different than Indians or Japanese. I don't think that does much for most to 'prove' or 'show' speication. I could be wrong, but that is how I see it. At the same time you have some people like Behe who does believe in speciation but denies that the origin of life could happen at a biochemical level without outside intervention.
They probably also don't live as long due to poaching, thus their tusks are shorter because they haven't grown out as far.
Sounds more like unnatural selection to me. Would the development of domesticated animals be considered evolution? Potbellied pigs? Miniature horses?
Yes. Evolution is modification by descent. Or, changes in population alleles over generations. Speciation is just one subset of this. The op is an example of this. Also, "micro evolution" is non science, just an ID term. Genetic change is genetic change.
Speciation occurs when enough genetic differentiation accumulates between two populations that they become reproductively isolated. This story isn't about speciation; rather, it concerns selection acting on a phenotypic trait (tusk length) to modify that trait across generations. Selection can lead to speciation - if two populations face different selective pressure so that each evolves differences that make them reproductively isolated.
Yes, the development of domestic animals is evolution - evolution by artifical selection. Darwin spent quite a bit of space in the Origin of Species talking about artifical selection in pigeons, horses, and others. The change in the elephants wouldn't fit the definition of artificial selection since the poachers aren't selecting for the resulting phenotype. Rather, shorter tusks is an unintended consequence of predation by poachers on elephants with longer tusks.
I agree that what is going on here falls within the realm of the term evolution, just as any type of artifical breeding is evolution. But I don't understand how the term 'micro evolution' isn't science, and is somehow a term invented by ID foks. I was taught the terms micro and macro evolution starting in junior high about 20 years ago long before the idea of 'intelligent design' came about. (at least long before the term ID.) As I recall these terms were used in our science textbooks, but maybe I just didn't realise how political they were at the time. I still do believe that there is a VAST difference scientifically between genetic changes within a breeding population, and genetic breaks which cause there to be a seperate breeding population. Something I still haven't seen evidences of.
Why is this artificial selection? What's unnatural about it? THEU: The terms "microevolution" and "macroevolution" exist without any scientific merit. Their sole purpose is to sow seeds of doubt about the veracity of evolutionary theory. As far as science textbooks, creationists have been censoring and polluting science curriculum long before they took on the politically expedient guise of "Intelligent Design". And as far as not seeing "evidences", I wonder what evidence you're looking for. Why would reproductive traits be immune from the evolutionary processes to seem to acknowledge occurring?
groverat, At some point an offspring will no longer be able to mate with the parent (or their generation) So who would the offspring be able to mate with? A sibling who has the same genetic difference? Or is there the presupposition that others of the same species would spawn a new species close enough for the first offspring to reproduce with?
So then is management of whitetail deer in south texas and other areas evolution? The fact that it is occurring only due to human pressures make it less evolution to me and more look at what our impact on the world is.
A species is generally considered a group of organisms that can reproduce with each other. A sub-species is something like a color variation, or a "race," which may be a geographically separated group of the species which develops different traits, but remains genetically able to reproduce with the other race of the species were they able to find each other. At least this is the definition of species as I understand it when applied to birds. I suppose the elephants developing small tusks could be called some form of evolution, but it certainly is not natural selection, it is artificial selection, or something like that. I wouldn't consider introduced species due to human direct or indirect involvement to be natural selection. More like a catastrophic event, similar to an asteroid strike on a wide area, or global warming, or an atomic blast on a species habitat.
The concept of species isn't hard-and-fast. Some species don't interbreed (e.g., humans and dogs), some interbreed but produce infertle offspring (asses and horses, the mule is a hybrid, not a subspecies), and some interbreed and produce fertile offspring (e.g., tigers and lions - only one gender of the hybrid is fertile, by the way). The degree of reproductive isolation is proportional to the time since separation. Most biologists accept some form of the idea that a species is characterized by some restriction in geneflow between it and closely related taxa. That restriction in geneflow isn't necessarily absolute.
Yes, for a species to be considered bona fide, it produces non-sterile offspring. But some separate species do interbreed and produce hybrids, like tropical parula and northern parula warblers, several duck species, and others. The lines can get murky when trying to differentiate one species from another sometimes, when you have intergrades, subspecies, races, hybrids, similar species separated by a geographic barrier long enough to become a separate species, things like this. This fact can make bird-watching tricky. Ornithologists are always doing studies to determine if some species is really two or more species, or if some similar species are really the same species. Recently, Canada geese were split into two species, I guess they were found to not overlap in reproduction-one species is now called cackling geese.
