Evolution and Human Traits

If part of evolution is to carry on the positive traits and characteristics of a species to enhance them, how come we don't have tails and the ability to easily swing from trees (or man-made structures)? Or strong jaws with sharp teeth? Or night vision or some sort of sonar? Nature didn't know that we'd eventually have cars to get around, or tools, or night vision goggles or lights to see in the dark.

 

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You're being facetious right?

 

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Every bodypart consumes energy, so anything we no longer need will dissapear in time.

"During adaption, some structures may lose their original function and become vestigial structures.[83] Such structures may have little or no function in a current species, yet have a clear function in ancestral species, or other closely-related species. Examples include the non-functional remains of eyes in blind cave-dwelling fish,[84] wings in flightless birds,[85] and the presence of hip bones in whales and snakes.[86] Examples of vestigial structures in humans include wisdom teeth,[87] the coccyx,[83] and the vermiform appendix.[83]" ~Wikipedia http://en.wikipedia.org/wiki/Evolution

"Biologists have evidence of many examples of decreasing complexity in the record of evolution. The lower jaw in fish, reptiles and mammals has seen a decrease in complexity, if measured by the number of bones. Ancestors of modern horses had several toes on each foot; modern horses have a single hoofed toe. Modern humans may be evolving towards never having wisdom teeth, and already have lost the tail found in many other mammals - not to mention other vestigial structures, such as the vermiform appendix or the nictitating membrane." ~ Wikipedia http://en.wikipedia.org/wiki/Biological_devolution

 

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Because it's a more successful strategy to grow a large brain. With this we can figure out tricks to hunt nocturnal animals, or make spears to take the place of teeth. We are still good in trees. We are probably so numerous because we started to invent things like tools and language. Some of our ancestors didn't do these things and ended up chimps with strong jaws.

 

Read Finding Darwin's God... it will explain it all in there

 

Some birds (cave swifts), but in much simpler form.

Mammals have excellent ears - really much better at picking up sound than most others, on average. That and the extra brainpower are important for sonar.

Sonar, like radar, announces its presence and location at much longer range than its usefullness extends. For a relatively slow, land-fixed animal with enemies of its own, that presents obvious problems.

 

Don't barn owls use a form of sonar?
The flattened area (dishes) around each eye are used to focus the echoes, AFAIK.

Just found this:
http://members.fortunecity.com/anemaw/otherultrasound.htm

 

Okay, so I guess my real question is this: how does nature know what traits to keep and which ones are/will become useless? In that case, how does nature "know" anything? For a creatures tail so slowly shrink to disappear over millions of years, doesn't something need to be switched in our genetics? Who/what does the switching? It couldn't have been a planned change as the evolution depends on the success and environment of the animal, so how do these changes come about?

Or am I looking at the scale of all this all wrong?

 

Nature doesnt know anything.
If the tail is not needed (the tail doesnt influence survival an any way) it can dissapear when the population somehow needs to conserve energy (the useless tail still needs energy). The individuals with a smaller tail then have more energy available for other bodily functions than the ones with a large tail. There is also something like sexual selection (which is selection for any trait that increases mating success by increasing the attractiveness of an organism to potential mates) which might have something to do with things like tails dissapearing.

If you genuinly want to know about the evolutionary process, why dont you buy some books on it or google it.

 

DNA mutates at a fairly regular rate. Thoses mutation that occur during gamete formation are passed on to offspring; as that one fertilized egg cell divides into every other cell in the child's body, the mutation is copied to each of those cells.

Those mutations are random, and most do nothing; most of the remaining mutations are negative to the child's survival. Of the tiny portion of mutations left, those which result in a shorter tail (and as Enmos pointed out), offer a little more energy available for running, or jumping, or chasing. Those which result in a longer tail do not help when the primate is spending most of it's life on the ground, more and more time spent walking long distances holding things in it's forelimbs.


Logic exersize with horrible, inaccurate math follows:
Let's say that a tail that is 1% shorter results in a 0.001% better chance of survival and reproduction in the living conditions at hand, and 25% of the population has such a tail. Doesn't seem very helpful, does it?

But when we consider that this rule applies to all 50 offspring per social group per year, over 1000 years, than we have 50,000 individuals to look at the 0.001% better chance *per individual* means that you could see a potential cumulative 12.5% reduction in tail size over that 1000 year period.

(This is a very poor and simplified example hoping to show how important time and rate of reproduction are to this equation. Don't try and over-think the math above, and it's not accurate to real-world examples)

 

This discussion has brought to mind a story I read once in Science Digest about moths in the Michigan area, or some industrial area where normally white moths began to be displaced by black moths. This enabled them to match the dark sooty bark of birch trees. In prior times, the birch was white and the white moths matched this. The period of time in which this industrial deposition of dark soot on trees was very short. It would be very interesting to know what percentage of moth offspring in prior times was black. It's interesting because birch trees also have black spots, so a small percentage of offspring with the dark coloration has a niche so there must have been a preservation of SOME black moths. When things switched there was probably a period in which the trees were grey, and I wish we had that data to know if there was a regular production of grey moths. It would be good to know total moth populations over this period, etc. I suppose my thinking about this relates back to frequency and genomic preservation of evolutionary history. I mean, does the giraffe genome maintain a certain percentage of dormant genes for shorter necked giraffes? Do they occur? But what if suddenly a new food source arose with abundance of food stuffs more easily accessed by short-necked giraffes? Obviously their necks would have to be long enough to access their mothers teats, but the question is rather about how variety is maintained in this "grey" area. What is the mechanism that preserves the off-chance useful characteristics?

 

Mutation is one. But i think what youre looking for is Frequency-dependent selection. This is the hypothesis that as alleles become more common, they become less fit. This is often invoked in host-pathogen interactions, where a high frequency of a defensive allele among the host means that it is more likely that a pathogen will spread if it is able to overcome that allele.
In your example of giraffes this could mean that if all giraffes have really long necks there is a niche for giraffes with somwhat shorter necks.
Also gene flow is a candidate. Gene flow is the transfer of alleles of genes from one population to another.
Other giraffe populations might have a slightly different environment with smaller trees. You get the picture.

 

If you look at nature as a separate universe that's merged with our existence then it helps to see it in 3d. Picture two realities separated by a wall they can hear eachother but have never seen eachother.

Nature reacts to what it can perceive of our needs in a limited capacity but can't see the whole picture. It interprets the data similar to hearing a story from a third party. That's why it doesn't always adapt fast enough and in many cases biologists will tell you how your own body reacts quite stupidly from it's simple lack of knowledge, such as the inability to cure itself from HIV .

 

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Nature doesnt react to or interpret anything.

"Nature reacts to what it can perceive of our needs in a limited capacity", this sounds like pure arrogance on your part.. please explain what you mean.

"how your own body reacts quite stupidly from it's simple lack of knowledge".
Firstly, a single organism cannot evolve, its populations that evolve. Secondly, the body doesnt know anything.. and it cant be stupid.

Please pick up a book about evolution and/or genetics.

 

sigh..rote learning is not the only way now is it? a few blind spots a possibility.

Nature does react constantly. That's why it's not conceptual enough to think ahead or plan ahead for possibilities.

 

You are personifying nature.. its quite ridiculous.

 

Excuse me? Didn't the thread starter ask why we don't have the strongest features that nature has evolved? That's because nature can only adapt to it's immediate environment, that's why animals and humans die off when exposed sudden changes because it can't adapt fast enough.

That's why we don't have the most efficient vision because nature is essentially reactive versus say an eagle. If you are in an environment that does not support the need of a higher functioning trait, it will not evolve it even though it theoretically is beneficial. It's stingy and even lazy in it's own process.

 

Now that makes a lot more sense.
Maybe you just worded it in a loony way before

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