Posts Tagged ‘social’
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How much must a species change for it to be considered a new species?
I was thinking about evolution and mutations but if a human child is born with a mutation like an extra arm/leg etc., it is still a human.. How much must a species change to be considered a new species?
Don’t forget that it is the *SPECIES* that changes, not an individual human.
Thus no individual born, no matter how totally “different”, constitutes a new “species.” At the very least, that individual needs to be able to mate with other humans in order to continue its own traits, and so that individual, by definition is the same species.
The answer is that if you just consider one species changing through time, there is no “line” at which it becomes a new species. This is precisely why scientists have lots of debates when they discover a new fossil about what to *name* it. (Is it a “late Homo habilis” or an early “Homo erectus”?) It may be clear that they are physically different enough to be considered separate species … but the exact dividing line in time where one species “ended” and the next “began” is not always clear … especially since populations of the first species can continue to live long after the second species has branched off.
What is far more clear is when a single species branches into two species (called speciation). We don’t need fossils to see this relationship. The answer is simply … however long it takes for two populations to have changed enough *genetically* to be unable to interbreed and produce fertile offspring. At that point they are two separate species … because any hybrids (if any), crosses between the two species, have no way to continue the species.
Note that this may or may not involve significant changes. Chihuahuas and great danes are *very* different physically, but are sill technically members of the same species (because technically they can still interbreed and produce fertile offspring). But many species of insects can be absolutely indistinguishable, but are different *species* … they cannot interbreed (there are at least seven different species of the anopholes mosquito that have been genetically identified as separate *species*, even though they are physically indistinguishable).
So don’t get confused that it’s all about “big” changes. Sometimes tiny indistinguishable differences can still be considered separate species, and sometimes huge obvious differences are not enough to produce a new species.
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