Steph

I never asked if we were two different species. If you stuck a bunch of whites in africa and let them evolve out for a couple thousand years would they start becoming black? If you took a bunch of blacks and let them live in greenland or upper canada for thousands of years, would they start to turn white? Are there any white african tribes? Are there any black Eskamos....im sure I spelt that wrong.

In our world, it doesn't matter anymore. Vit. D deficiency is irrelevent in developped countries so darker people won't die of it (no natural selection). second, skin cancer when caught early is rather easy to cure, so if you are pale and live in an area at risk (like australia), you just go see the doctor and get checked often. of course, you would have the odd death, but that wouldn't be statistically significant. Of course, going to underdevelopped countries, you have a different dynamic, but we are talking about thousands of years of evolution, whereas the time gap between poor and rich countries is at most 100 years (and i think i'm exaggerating).

well then we must always be sick then cause we always have bacteria in our blood. i asked my friend who is doing 4th year microbiology and he said that blood is a really good breedingground for bacteria although the white cells do fight back in a body. BTW if blood was always sterile then how do we get sick.

All that your friend said is true but we are talking about Normal Flora, bacteria that won't usually cause disease. I may have worded it badly but what I meant is that bacteria shouldn't usually be found in the blood. This doesn't mean that no bacteria can grow, just that if they do, you are in trouble.

Also, blood is not always sterile: for example, you can get cut and bacteria like C.tetani enter your bloodstream.

btw, I am also a microbiologist.

I always thought dogs could see color just like we do. Now I know dogs have dichromatic color vision. Makes me see dogs in a slightly differen't light.

 

Is this how people become color blind? When one of these pigments is missing or damaged?

You have three kind of cells (cones) that detect light at a specific wavelength. So to have a color deficiency, you can have:

-Missing cell types (VERY rare)

-The peak wavelength that the cells are sensitve to are shifted, or you have decreased sensitivity. for some reason, insensitivity to blue light is also rare.

blood can contain bacteria when your not sick. infact it always has a few microbes(not necesarily evil ones) by microbes i mean foriegn(spellings gone today methinks) bacteria.

Hi... I'm new here, but I just want to add something.

Blood is sterile. There has been reports of bacteria and other microorganisms in blood, but those are controversial at best. If you aren't sick you shouldn't have any bacteria in your bloodstream. this said, I also think that in nature, you can never say never so...