I was talking about this in a related thread, but I thought of having a new thread. So here are my questions related to the senses :
1> Vision : Have our vision capabilities changed over the years with respect to the spectrum of observable light, intensity and persistance of vision. I believe it will be an evolutionary example to a predator/prey to be able to observe low frequency light (near IR) in the forest, but we humans don;t need it. So has our vision changed ?
2> Hearing : Is there any change over the years on the frequencies of sound we can hear and/or their intensities ? Again being able to lower or higher frequencies may be a evolutionary advantage.
3 > Smell : I don’t know if this can be objectively measured. Maybe by ppm or ppb of known odor in the air. Has that changed ?
4> Touch : Donno if our skin can withstand higher temperatures. Certainly (?) hair on human body seems to be on a decline, so will hair become a vestigal organ ?
5> Taste : I think this should be same as smell - say like detecting a known taste at the ppm levels. Has that changed ?
Sense of smell dropped off seriously when we became bipedal.
When you are upright, away from the ground, you are away from the chemical traces that comprise an odor. The chemicals are, after all. denser than the air around them.
If we were on all fours again, our sense of smell would be about as good as it was when we were mere animals.
since we last shared a common ancestor with the other great apes, basically not at all: all chimpanzee and gorilla senses seem to be pretty much identical in acuity with our own.
in fact, we’re pretty similar to all other primates in the balance and quality of our senses (and exceptions to this, like nocturnal Madagascan primates which have comically large eyes, are clearly the ones with the derived feature).
of course, how we interpret the sensory information we receive is something else altogether…
since the last common ancestor we (the primates) share with all other placental mammals (some kind of small shrewlike creature), there are clearly significant differences, basically
greatly improved (and binocularised, ie both eyes forward facing) vision, especially colour vision
hugely reduced sense of smell
disimproved hearing (especially at high frequency and in terms of direction detecting)
and a sense of touch which is greatly altered by the loss of vibrissae (whiskers).
as for any change in the quality of our senses going on at the moment, there really aren’t any significant evolutionary pressures acting on humans as a species to promote such change.
1> Vision : we’ve used our ability to discern green and red (ripe fruit) to aide in survival for millions of years, I can’t see how this would be weeded out in our short time out of the woods. It does seem that with the onset of civilization and invention of glasses that poor vision would no longer work against one’s survival, thus allowing poor vision genes to propogate.
2> Hearing : my guess, again, is that it is worse than our ancestors, since we no longer rely on hearing for survival.
3 > Smell : something like 70% of our olfactory genes are mutated beyond function, this could have been an advantage to allow a bunch of smelly humans to live in a city without being driven crazy due to sewage, garbage, and body odor.
4> Touch : I’d guess our sense of touch is good as our ancestors, possibly better. For one, we have less body hair and are thus more sensitive. Also, using our fingers to do small everyday tasks is essential.
5> Taste : tase is probably as strong as ever, if not stronger. It is essential to select non-contaminated foods for survival, and cooked meat. It’s possible though that our ancestors were able to tolerate a much wider variety of tastes since they didn’t have the luxruy of being so selective.
Ok - I wanted to know both - changes since homosapiens started out - and also after the industrial revolution. The former because i think that may be considered the dawn of humans and the latter because the industrial revolution brought about a significant change of lifestyles.
Look at vision. One of the major properties that is noticed and in fact draws attention in one’s peripheral vision is motion. This makes sense in the wild: seeing the lunging tiger in the corner of your eye might give you the chance to roll away.
Well, since the Industrial Revolution, the rate of myopia has skyrocketed in developed countries. Nobody seems to know why, but any number of things, such as diet, artificial lighting, and reading have all been blamed.
We need to think about basic information regarding evolution as it pretains to a species with a large breeding population…which for humans now is pretty much the entire human population.
Evolution occurs because of mutations resulting in traits that are selected for over the pre-mutation trait.
We no longer are living under the same conditions that gave rise to modern humans. The advent of agriculture, clothing, housing, medicine, transportation and other technologies serves to insulate us from many selective pressures that lead to modern humans.
One type of selection is sexual selection, where mates are chosen on some feature that signals the ability to reproduce, or to be the most desirable choice for a mate. (Think of the peacock’s tail signalling robust health on the part of the cock to the hen). This type of selection may be working in humans now. Do certain males or females have more children who survive due to the attractiveness of the parent?
Another type of selection might be the ability to withstand exposure to various environmental assaults like pollution. I don’t know of any expamples of this being studied or discovered in humans.
Is there any selection for mates that takes into account the sensory abilities of the potential mate? How common is this in the 5 or 6 billion population?
Just as humans are not losing their legs because they don’t walk as much (legs being part of the genetic code that we inherit),there doesn’t seem to be any selection going on to alter the state of human sensory capabilities.