I wouldn’t argue with that. I should have specified survivability as a factor that would increase the rate of divergence, but not substantially changing the time scale. Drift, which may or may not occur in this scenario, could certainly result in distinctive genetics in the time scales we are now talking about. I’m not sure if humans and fruit flies would be affected the same way though.
And I’m assuming a reasonably large population and diversity of human genes as well. Otherwise we’d be talking about the conditions associated with genetic engineering.
That still probably falls significantly short of the mark, since human generations are much longer than those of comparably-sized mammals. Horses, for example, can start bearing young at four or five years, and dogs at about one year, but humans can’t even start until roughly some time in our teens, and can keep going long after most mammals would be dead.
I think we are still evolving, e.g. height, intelligence (I fear we’re going the wrong direction,) etc.
However, I don’t think we’ll ever become two different, non-replicating species unless three of the previously discussed conditions occur: a very long period of isolation, a very extreme geographical change to one of the groups, and a lack of genetic exchange between the two groups during that time period.
I think we’re evolving in a technical sense, but not in a consistent, meaningful way.
But even if we were evolving as you suggest, I’m curious to know why you fear we are going in the wrong direction.
Usually, when calculating this sort of thing, it’s done in units of 2N generations, N being the size of the population, which makes 2N the number of chromosomes involved. The smaller the population, the faster genetic drift can cause new alleles to move to fixation. Even so, we’re talking hundreds and hundreds of generations at a minimum.
But genotypically, if humans were dogs, we’d all be the same breed.
Since we’re supposed to posting factual information in this forum, I’m going to call bullshit on this. There is no “wrong direction” in evolution.
Ditto here. This is no such thing as a “consistent, meaningful way” in evolution. It just happens. It only looks consistent and meaningful after the fact.
Evolution in a consistent and meaningful way can be measured by accommodating to environment. It’s not like a squirrel wakes up one day and says, “You know, it sure would be nice if I had wings.” But squirrels jump from tree limb to tree limb, and over successive generations the ones who succeed better live longer and reproduce more. So maybe the ones that do have slightly looser skin, and their offspring retain that, and they in turn have slightly looser skin, so that when they jump, it spreads out, giving them slightly better gliding.
It is consistent in that over many generations you can track the trend to looser skin that becomes an aid to gliding, and it is meaningful because it leads to the ability to glide farther and therefore jump farther, either to get to new food sources or escape predators or both.
As opposed to population variation that drifts around but doesn’t change much across multiple generations. The beaks get bigger, then the beaks get smaller, but no trend over time.
John Mace said:
“Wrong” is a subjective determination. From a human perspective, lowering human intelligence overall can be evaluated and judged as “wrong”. You are correct, evolution only cares about what survives, and doesn’t measure “right” or “wrong”.
Ok, but I was trying to make a more specific point about humans in particular. There are fewer selection pressures that are on us, thanks to medicine, agriculture etc. And we’re changing our environment and society too fast for evolution to keep up with.
So even those selection pressures that are there are likely to shift in importance or be removed outright, long before the kind of significant, “Homo superior” changes of the popular imagination.
This is quite an interesting question. If you look at the history of homo sapiens, it would seem that we match the pattern of adaptive radiation. Starting 50,000 years ago there was an explosion of the human population to nearly every corner of the globe, allowed by some adaption, which was probably an “advanced ability to make tools”.
This is such a huge advantage that it would be like the first bird to have true flight. The population would have exploded and spawned a huge new number of bird species as they filled new ecological niches.
Assuming we don’t destroy ourselves we will eventually speciate as all other successful organisms did. When that happens, it would be inaccurate to call one better or worse. It would be like saying the Mangrove Finch is superior to the Warbler Finch.
The difference is that various finches were separated from each other in differing environments for long periods of time. Given that humans are smart enough to avoid being separated for the pre-requisite giant periods of time unless they want to be, it seems unlikely we’d speciate in the same way. If you scatter a bunch of humans across an island chain, sooner or later they’re going to start building boats and marrying/boinking/raping eachother.
Not until the year 802,701 AD.
Given that speciation has been going on for several hundred million years, I find it difficult to draw a line in the sand in year 2010 as the point where it stops forever. Homo sapiens are impressive, but just another (successful) organism in our planet’s history. As recently as 15,000 years ago Neanderthals and Homo Floresiensis lived at the same time as us. From a cosmic point of view, are you really comfortable in saying that it will never happen again?
Furthermore, populations like the Sentinelese and the Yup’ik seem quite content by themselves and its difficult to imagine how those two would ever interbreed.
Neanderthals died out about 28k years ago, just for the record.
Also, it’s Homo floresiensis. Species name isn’t capitalized.
They don’t need to. It doesn’t matter if every single subpopulation on earth manages to breed with every other subpopulation on earth. They simply need to not be completely isolated. If population A interbreeds at some low frequency with B, which does the same with C, all the way to that rebellious little Y teenage girl who gets pregnant with that handsome hunk from Z who just refuses to play by the rules, then you get gene flow between all these populations, which is all that’s needed to prevent speciation.
Given the time scale we are talking about (1M years or so), it’s very easy to imagine how those two populations would interbreed.
We’re heading towards 7 billion people with a high degree of genetic diversity on the planet now. It would take a highly selfish, beneficial genetic structure to cause a species change in humans here on earth. If we travel to the stars or get a reproductively segregated grouping some other way, and maintain the same kind of population levels and diversity, even a million years may be optimistic for the emergence of a new species. Seems more likely that genetic engineering would affect us before then.
Yeah, like I said in my earlier post, on the time scales we’re talking about for speciation to occur, genetic engineering is almost certainly going to be a bigger factor. Even if we crash and burn several times, having to re-invent civilization, there’s still plenty of time for that to play out in a million years.
We should get started on that. Any suggestions?
I’d bet that 99.9% of speciation events have occurred through the “classical” mechanism: isolated populations slowly accumulating genetic differences until they can no longer produce viable hybrids.
However, it’s possible to imagine “instant” speciation occurring. Some mutation might make an individual infertile with any other not having the same mutation. Like an Rh factor, but worse. Adam and Eve mutants, probably siblings, might succeed in founding their own species. It’s very improbable, but, given the millions of species that have existed on Earth, I’d be very surprised if it hasn’t happened numerous times.
As others have mentioned, humans are very mobile so geographic isolation is unlikely to lead to speciation. And cultural isolation is too short-lived. But - who knows? - it still might happen.