Let me take a stab at answering your question. Yes, there is/was evolutionary pressure for us to be able to handle water right out of the lakes and streams. But, there is evolutionary pressure for the nasties to be able to infect us. Whenever one side (us or the nasties) gets ahead, the other is under more pressure to adapt. No organism evolves in a vacuum.
I also question your assumption that homo sapiens are noriously poor at handling un-treated water. We are more likely to notice when one of our own falls ill. In birds that flock, when a member is noticeably ill, it is cast out for the good of the flock. Loners quickly die off. It could be that the ill ducks are just not around long enough for you to notice.
For Xmas, get Triskadekamus a good pair of glasses so that he can better spot tongues when they are firmly planted in cheek*.
Look, jack, the source I quoted was an Internet list. That was a dead give-away as to the veracity even for the uninitiated.
And the tag line is true: We DID raise ducks. We DID have a pond, and I KNEW that factoid was a load of horse hockey a long time before it ever appeared in this column.
*This is in no way a reference to another subject that frequently comes up on these boards.
The big difference between ducks and humans isn’t that they can handle stuff better than we can… The biggest difference is that they don’t care as much when they don’t handle it, or at least, don’t show that they care in ways that we recognize. If you have a community of a hundred ducks, and five die from contaminated water, hey, you’ve still got 95 ducks! On the other hand, people aren’t likely to take it lightly if five humans die. Hence, we develop water purification systems to protect those five.
The reference was for anyone who did not know the truth. After all, it is ignorance we are fighting here. Perhaps I should have mentioned that ** everyone ** :rolleyes: knows the fact that duck quacks do echo, but instead I just made a second sarcastic comment, and made it a hyper link.
Tris
Note to self: send thank you note for the nice new glasses, and get hammer boy a new tube of skin thickener.
Exactly. That, plus our longer lifespan increases the chance of ingesting a nasty parasite during an individual’s lifetime. Water treatment is a balancing of risks (disinfection presents its own chemical risks).
Humans were able to survive for 100’s of thousands of years without water treatment (millions of years if you count all homonids).
evolution as a process is blind to the final result. it does not take into consideration where the organism is going to be eons from now.
why do we not have immunity to many water borne diseases? because of human ingenuiuty. if not for our larger brain capacity and forsight, we’d would not have stumbled across the idea of treating water before imbibing it.
at what cost does this ingenuity come? the absence of an ‘iron stomach’
if a million people drank tainted water and only 3% have intrinsic defenses against waterborne diseases, those 3% will survive and proliferate their genes to subsequent generations, passing on the trait. you would then have a populution of resistant people. however, do NOT forgwt the fact the water borne parasites are also biological beings as well are are subject also to the process of natural selection. it’s an on going arms race. as we develop immunity, so does the parasite develop and immunity to our defences.
"Yes, chalice, you are correct; evolution WOULD select FOR the ability to drink untreated water, rather than for its absence. Our ancestors–homo erectus, etc.–were almost certainly able to handle untreated water. However, as we evolved into homo sapiens (i.e., became more intelligent),
it’s quite likely that we figured out that by BOILING the water (or avoiding bad water sources, etc.) we could keep ourselves from getting sick. Therefore our digestive systems stopped evolving (in that respect, anyway),
simply because they no longer had do. The bacteria, by contrast, continued to evolve, to the point where now they are far better at making us sick than we are at fighting them. As a result, we can no longer handle untreated
water. Ducks and their ancestors, on the other hand, did not evolve as humans did, and never became intelligent enough to figure out that they could keep from
getting sick by treating the water. They and the water-borne bacteria thus evolved together, each trying to ‘outsmart’ the other, so that now, ducks CAN drink untreated water.
I think several of us have made ostensibly these same points; I hope this
summarizes them somewhat.
(I will also note but not address DrMatrix’s excellent point that we notice
when humans die, but not when ducks do. That’s a separate issue.)
What I’m curious about is this: if I, as an American, moved to Mexico and lived there for 10 years, would I eventually be able to drink the water? Or would it be my children’s children’s children who could drink the water? I’m not clear on the nature of Mexican water-borne parasites; is the ability to handle them a matter of adaptation or evolution?"
Well, one of my neighbors growing up was a first- or zeroth-generation Mexican immigrant (depending on how you count it), and he had no trouble at all drinking Cleveland water, so one assumes that tolerance to American water nasties, at least, can be acquired by an individual. I suspect that the situation’s at least somewhat symetrical, as AWB mentioned.
While it is true that we are constantly evolving it take a long time to change noticeably. I don’t think our immune systems have had time to change since we started treating water.
I don’t know for sure, but I’d bet that in less than 10 years you would be pretty much immume. One of the benefits of breast milk is that it passes antibodies from mother to child. In an environment where the mother has developed an immunity, she can pass this on. It is an adaptation that can be passed on.
I think the reason for these facts is that widespread water contamination is a geologically recent phenomenon. Many water-borne microorganisms—giardia, for example—require a person to ingest a certain amount in order for the disease to become established in the host. When humans were relatively scarce, concentrations of these microbes in surface water was too low for large numbers of people to become infected. The recent geometric rise in human population caused the endemic contamination of drinking water. Therefore, we now have to purify it.
I would surmise that many of these diseases are human-specific, so ducks can drink untreated water with relative impunity. On the other hand, if ducks undergo a similar population explosion—and, personally, I think this is exactly what they’re planning—we would see a corresponding increase of water-borne, duck-specific diseases.
Mauve Dog, this is what ornithologists say about vultures…
“Vulture digestive acid is so strong that it readily processes even the most putrid substances without giving the bird so much as a
belly ache. In fact, these birds are credited with reducing the occurrence of disease because they eat diseased animals and
prevent sickness from spreading in this way. Their digestion destroys harmful agents such as anthrax, botulism and cholera.
These diseases can decimate human and animal populations if allowed to spread.”
Dumb Ox
I hadn’t thought of that. The increasing density of humans causes the water to breed more nasties. It makes sense. This would imply that where there are higher concentrations of people, the water is more harmful to humans, but not necessarily to ducks and I think this is probably the case.
