If speciation can happen in 'low level' species, why not humans?

New (genetically new) species have arisen in historical times. For example:

* A new species of mosquito, the molestus form isolated in London's Underground, has speciated from Culex pipiens (Byrne and Nichols 1999; Nuttall 1998).

* Helacyton gartleri is the HeLa cell culture, which evolved from a human cervical carcinoma in 1951. The culture grows indefinitely and has become widespread (Van Valen and Maiorana 1991).

* A similar event appears to have happened with dogs relatively recently. Sticker's sarcoma, or canine transmissible venerial tumor, is caused by an organism genetically independent from its hosts but derived from a wolf or dog tumor (Zimmer 2006; Murgia et al. 2006).

* Several new species of plants have arisen via polyploidy (when the chromosome count multiplies by two or more) (de Wet 1971). One example is Primula kewensis (Newton and Pellew 1929).

Update:

In evolutionary biology today, macroevolution is used to refer to any evolutionary change at or above the level of species. It means at least the splitting of a species into two (speciation, or cladogenesis, from the Greek meaning "the origin of a branch") or the change of a species over time into another (anagenetic speciation, not nowadays generally accepted). Any changes that occur at higher levels, such as the evolution of new families, phyla or genera, are also therefore macroevolution, but the term is not restricted to those higher levels. It often also means long-term trends or biases in evolution of higher taxonomic levels. - So, if you're gonna say 'well that's not macroevolution, you are using your own Creationist definition of a scientific term, not its actual definition.

Update 2:

See http://en.wikipedia.org/wiki/Evolution_of_the_hors... also for 'transitional' fossil/bone records. Would you call a tiny horse with 4 toes the same species if it was alive today? From the same family, maybe, but totally different.

Update 3:

'Titanium...' - I believe in the generally accepted fact that humans have not changed as quickly as any of these examples. They are purely examples to illustrate how species can change. Humans, of course, as you say, would take longer due to their lifespans and slow birthing cycle. I also believe in the continental drift, so continents would have at one point, millions of years ago, been altogether, then gradually separated into the continents we have today. Humans, and many other animals species (or indeed their ancestors) may well have lived in one place at a certain time, then as continents split, certain groups would have ended up in totally different places, but likely evolved from the same common ancestor/been a similar species at one point in time. This continental drift theory is supported by the similarity in many species in South America and Africa, and in their shapes, that seem to 'fit' together.

Update 4:

And Africa and Denmark are linked by land at any rate, so perhaps at one point they all lived at the North of Africa/South of Europe (as we know them today.)

Update 5:

Why are people taking this question differently to how it was intended? I am not saying that the human species has changed as QUICKLY as others, merely that speciation can happen. I am well aware that human speciation would have to take millions of years.

12 Answers

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  • 1 decade ago
    Favorite Answer

    We are destined for a 'higher level'?

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  • Anonymous
    1 decade ago

    The reason that speciation does not occur in humans at the rate that it does in "low level" species is that there is a vast difference in the complexity of the organism. The fact that the human system is mutable in the same way that the lower organisms' is is shown by the frequent and rapid adaptation of the human immune system as seen in localized immunities vs. vulnerablilities. For a transformation of the scale described in the examples cited, with the increased complexity of the human example there would be required an increased time span for the change to happen. Since the human organism is about 10 billion times more complex than a bacterial organism one can "do the math" to ascertain how much longer it would take.

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  • Anonymous
    1 decade ago

    Whereas all other life has evolved into different and new forms, humans have de-evolved, from a long living, highly intelligent species to what we are now. Of interest, things changed with the generation born in 1900. They are the first generation in over 1000 years where the majority had a natural life span longer than 46 years. This is the generation that was of the age of understanding at the time when the signs of the second presence of Christ began being fulfilled.

    A contributing factor could be the Spanish Flu, named such because only Spain's media reported on it. It targeted only the young and healthy, killing more solders on ships going to WWI, than all those who died in action.

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  • Anonymous
    1 decade ago

    I'm only a 4th year biochemistry student, so you'll have to forgive my ignorance of some topics.

    It seems that in some schools of thought Homo sapiens sapiens (modern human beings) are split into some sort of sub-racial categories, even in the scientific community. This just doesn't seem logical to me inasmuch as you cite organisms with incredibly fast gestation and short life-spans. Of course those will rapidly change and by their very nature they will be adapting to their environment.

    Humans, on the other hand, have a relatively long lifespan, as far as mammals go and we simply cannot make such radical changes so quickly. Yes, people in hotter climates tend to have offspring with darker skin, etc, but that is a far cry from going from human to a tiger or other such radical change.

    The most isolated African tribesmen have the same gastrointestinal enzyme that digests milk proteins as the blonde-haired north people from Denmark, and yet the two people couldn't be further from each other. Yet those between the two don't seem to possess the same enzyme. Is it possible the exact same molecular composition of the enzyme just "happened" to occur? If you believe so, you might want to review your physical chemistry notes.

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  • There's no reason per se why humans couldn't speciate. Currently, though, the modern ease of transportation probably serves to stir the gene pool more than well enough to prevent it actually happening. Before that simple human curiosity caused enough wandering & trade to mix things up.

    Once we colonize the moon and eventually Mars and other planets and extraterrestrial locales, though, we will have greater potential for genetic isolation. Even with the widely different conditions those locales would introduce for the separated populations it would take a while.

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  • 1 decade ago

    There is no reason. There is no genetic mechanism to prevent a speciation event from subdividing the human population. We are about 10,000 generations from the start of the Homo sapiens line and I am not aware of any selective pressures likely to result in sudden shifts, but there is no knowing what the next great step will be.

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  • Gustav
    Lv 5
    1 decade ago

    It takes a lot of years and I think the biggest problem for that now days is that every time there is a mutation in someones genes it is considered a defect, so there is no way it can reproduce and be considered an advantage. Didn't you read the news a few months ago of a baby born with a third arm? Doctors immediately operated it.

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  • Anonymous
    1 decade ago

    You asked why people are taking the question differently than you intended. Look at the wording. "Why not humans" is meant rhetorically but it sounds like you are asserting that it can't happen in humans. When I first looked at the question it sounded like you were saying basically "why is it that this happens in blah blah but it doesn't happen in humans in the same way?" The assumption is, since this is posted in the R&S section you are an anti-evolutionist trying to poke holes in the idea of human speciation (that is the atmosphere around these parts).

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  • fette
    Lv 4
    3 years ago

    it really is called faith. How come the international is so fantastic and complicated if there became no speciation? as well there is an evidence coming quickly. i'm writing a e book that announces it truly is actual. So there you bypass, infidel.

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  • 1 decade ago

    Humans are rather complex genetically, and new generations take a bout 20 to 40 years before they reproduce again, so it takes a logn while for mutations to become successful. Moreover mutations might be killed off, prevented from reproducing etc.

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  • 1 decade ago

    We are a bit more complex as a species, than a insect or a bug!

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