We the Hominids

Say Hello to our little Hobbit cousin.

It is a fascinating time to be the last Hominid standing as pointed out in http://www.pbs.org/wgbh/nova/beta/evolution/becoming-human-part-1.html The pieces coming together are simply amazing. Science can finally explain in great detail who we are. We are advanced enough to examine our origins carefully yet near enough to our Hominid kin to extract DNA from their bones. My mind reels when considering the fact we have been the only Hominid on the planet for a mere 28 thousand years.

As a boy I read the Conan the Barbarian books, set in a time before civilizations and shared with creatures not quite human. Conan was described battling the very beast that would one day become our legend. The tales were so provoking the author seemed to be taping into an almost genetic memory of the mystery of that time. An age where Homo sapiens grew up in a world cheek by jowl with Homo neanderthalensis, Homo heidelbergensis and Homo rhodesiensis. Imagine the wonder of being the first Human to encounter Homo floresiensis, our new little cousin.

This is probably why I am so enthusiastic to see the light of science shining on the path we took to this particular prominence. A prominence from which we can look back and appreciate the noble creatures that brought us to this point and made us who we are.

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Now, if we could only catch and kill the Bigfoot clan.
Hi Mike,

Yes indeed discoveries of extent species related to us journeying back through time are very interesting. From an evolutionary perspective it is intrigueing to muse why these species became extinct in the first place, maybe due to habitat loss, competition possibly from homo sapien ancestors, disease. As species tend to have niches in the ecosystem, ours being intelligence and adaptability it is also interesting to postulate how this evolved. Current Homindae include chimpanzees and bonobos whose niches are predatory but restricted to rainforest regions. Our ability and our ancestors abilities to adapt to new environments may be the reason why our species was so successful.

Hey Bex,

It is quite amazing. I just learned the Neanderthal were probably carnivores, talk about inflexible! The speculation that the use of fire is what allowed Homo Erectus to leave the trees forever. Our kind may have been sitting around camp fires for 1.3 million years. No wonder it is so captivating.

Given the number of hominid species that once existed I don't think our acenstors were all that surprised to see other humaniod creatures wandering around. We may have even traded with them, possibly gone to war with them. In the distant future there may be more than one species of hominid on the planet again, if we are continuing to evolve.
I am interested in how humans will continue to evolve. Could you lay out some mechanism that would cause this?
Well I'm not a scientist, but I speculate a lot so maybe I can offer something. It would depend on whether we'll still be able to travel across large distances in short periods of time. If we can sustain our technology indefinately, we may not evolve very much at all because of all the genetic drift we're able to create, especially in nations where it's common for people of different ethnic backgrounds to marry.

On the other hand if we're not able to sustain our technology at present levels populations will start to become more isolated, which will at least help unique mutations accumulate. On the extreme end of this senerio if our technology fails completely natural selection would start kicking in reletively quickly. Population levels would drop drasticly, cities would be vacated for lack of food, and people would have to start moving back to nature. Then I assume natural selection would proceed business as usual.

But I'm probably letting my imagination run away from reality. Small towns with self-sustaining communities are not going to be affected by this as greatly as cities. They may hardly be affected at all. People would have to adapt to more primitive ways of living but we would probably manage. These towns would probably take in pilgrims from the cities for a while, as many as they could sustain at least, but many would inevitably be turned away and forced to make a living in some other manner. Everything would be chaotic for a long time but eventually people would figure out how to live without modern technology the way we did for most of our history on this planet, so odds are we would have cities again, but in only in areas that can support them. Most natural selection would likely happen in areas where humans are isolated in small groups, in the extreme enviorments, and if conditions remained the same for a few hundred thousand years some populations might change enough to be considered new species.

Assuming we don't royally fuck up our situation on this planet with nuclear warfare or cause catastrophic damage to the enviorment I think it's highly unlikely that we wouldn't survive losing all our modern technology. We're adaptive little buggers, like rats.

To take it a step further, think about the basic body plan of the rat. There have been rat-like critters around since about the time of the dinosaurs. I don't want to sound human-centric, but I really do think the basic human body plan (which is also mostly the primate body plan) of big brains, dexterious hands, and bi-pedal bodies capable of a wide range of movement, from climbing trees to crawling down holes to swimming in the ocean, is one of the most aggressive adaptations in nature. I think we've got a lot of potiental.
Actually, homo sapiens are continually evolving just for the ones in "first" world countries natural selection isnt as big a pressure. This is due to the fact that random mutations happen everytime a new generation is born, so there will always be variation in a population and depending on what environmental or "new" selection pressures there are then they will select for individuals better adapted to this pressure. For humans in the third world natural selection is very much still relevant, due to famines, diseases and predation. This means that these humans will become better adapted for their environment, examples are increasing numbers of people are resistant to HIV, some are carriers but do not show symptoms. Other impacts, especially with climate change will include increased numbers of people able to survive longer periods without water or food etc.

If there are strong enough selection pressures in first world countries which would be possible still as these areas will be affected by climate change, then we see a gradual change in favour of those best adapted. As well as this there is natural genetic drift, whereby either sexual selection by females or other parameters means that populations will change over time anyway.

It does not mean however that people will one day fly, breathe underwater, be invisible or have super human strength as the selection pressures are not great enough. These feats will only be accomplished through genetic engineering over many generations. Personally I am all for genetic engineering to combat diseases and enable humans to survive long periods in space, it will be the only way they will stand loss of bone and muscle and that the human race will ever reach the stars.

So what do you think, is my explanation all encompassing or have I missed anything out??

Bex :)
I agree with most of what you guys are saying.

Bex, I have no problem with local adaptations being preserved. HIV is a huge pressure in some areas in the world and it is easy to see how natural selection could preserve it.

I'd like to raise the bar and define evolution a little more tightly for the sake of this discussion. First, I'd like to limit the definition to changes occurring due to natural selection only. Second the changes result in a new human species. Enough change so that if we bred with these humans the offspring would be sterile.

Outlaw, the environmental scenarios you draw could happen. OK, might happen. But what you are talking about is MASIVE depopulation of the planet. Small groups thrown into isolation for very long periods of time. The environmental degradation would have to be to the extent that these very small bands of individuals are just barely escaping extinction so that they lack the resources or population pressures to spread around the globe. Yet evolution is not guaranteed.

My thinking goes along these lines. Our minds are a game changer. Once we evolved our brain, massive physical change is just not required. We started out as small isolated bands of individuals with only rudimentary technology. When we moved north our skin lost pigment, we didn't evolve feathers or wool coats. We made them. As we moved east our skin pigments changed, eye shapes shifted. Local adaptations (sexual selection for this argument qualifies as natural selection). We made it all the way to the Americas over what? 190 thousand years? We changed very little.

Evolution through natural selection occurs when the environment changes you. When you change the environment, the bets for evolution are off.

Now lets go back to Bex's local adaptations, HIV survival for example. There is certainly a mechanism here, differential production of offspring. We will ignore the fact that infected people with no resistance can produce prodigious numbers of offspring. Yet the pressure is mitigated again because of our brains. A child can be born with HIV with no immunity yet survive to a reproductive age due to medication. This changes the environment that the genes compete in. Our evolutionary slight of hand steals advantage from a justifiably advantageous mutation (and a damn good idea). Not only that but there is all this DNA swapping going on with populations not under the same pressure.

I see local adaption as as bunch of drifting back and forth but never really getting anywhere. Thats the thing about evolution. Adaptations are not preserved because they are a good idea. Very beneficial adaptations can get washed out of the population because there is just not enough selection pressure.

Maybe in half a million years we will all be immune to HIV. However, if it happens it will take much longer than pure natural selection could achieve because our brains play dirty gene pool.

I don't know, that is how I understand it as of today. That could change tomorrow.




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