I never said the bug changed and the case of measles it is not a disease that wipes out a population. The majority of the population usually gets measles and then it moves on to another group. A few years later, the disease works it’s way back and infects those that weren’t exposed before. It is mostly children that get it although some adults who weren’t exposed before may catch it. The Native American populations were not big enough for the disease to move on and return.
Also your example of the Aborigines in Northern Australia was very interesting, but I never said that all small populated areas were the same. I believe we were talking about Native Americans.
My mistake. I assumed that when you said “A stronger bug may wipe out most or all people in the area, but then just die out” you were implying that such a mechansism has resulted in weaker bugs via natural selection.
No.
That was precisely my point. Measles is very much a disease that wipes out entire populations. Not the entire species, but there are numerous documented accounts of entire tribes, clans and villages being completely killed by measles. To the extent that any disease can be said to wipe out entire populations of humans measles is indisputably one of them.
Yes, the key word being those who weren’t exposed. Obviously no disease can kill those parts of a population that aren’t exposed to it. I’m sure there are many diseases on distant planets that could almost kill every human in existence. They are universally fatal diseases. They don’t decimate the human species because we are never exposed. That doesn’t allow us to proclaim that such diseases are not capable of wiping out populations.
Well, no.
Firstly we know from numerous examples elsewhere in the world that far, far, far smaller populations than those found amongst Native Americans were more than large enough for the disease to move on and return. Size simply isn’t a factor in this.
The reason I gave that example was that it shows that small populations are neither more nor less susceptible to such diseases. Despite your claims, size simply isn’t a factor. Travel, exposure to the disease and genetic diversity all play a role, but size simply doesn’t come into play. American Indians living in cities of over 10, 000 souls were decimated by European diseases, while Eurasians living in hamlets of less than 20 people were and are routinely unaffected. Aborigines living in groups of less than 10 people were similarly unaffected while Aborigines living in groups of several dozen people were decimated.
That’s the point before those examples. When you claim that size is a factor your need to be able to point to some example of where small populations were more affected by novel diseases. Of course no such evidence exists. All that you have done is said that Indians were more affected than Europeans, Indians generally lived in smaller cities, therefore small city sizes is a factor. You might just as well conclude that skin colour or language are factors. They are not, they are coincidental, as is population size.
Correlation does not equal causation. Indians were more susceptible to Eurasian diseases and often had smaller populations. That is very different from your claim that Indians were more susceptible to Eurasian diseases because they often had smaller populations.
What I said has been turned every which a way, so I rest my case with the above
showing that size of population counts.
I am not the only one that has been corrected. There is the question about humans using fire to keep predators away. This idea was criticized considerably, yet the following cite says exactly that.
kniz I have no idea what the relevance of fire is, but that first quote says quite specifically that it was isolation (ie the lack of travel I referred to in my firstpost) of small bands that was important, not the size of the bands. As I have already pointed out small bands elsewhere in the world that were not isolated were no more prone to the effects of these diseases than large bands.
It’s a simple neough question: if size is of any relevance why did small groups in Northern Australia and Europe not succumb to diseases, and why did large groups in Southern Australia and the Americas succcumb? The only common factor in whether a group succumbs is whether they are isolated, not whether they are small. Small bands are neither more nor less afflicted than large.
Hate ta tellya, but Chagas’ Disease is the trypanosomiasis brought to the new world when slaves were brought from Africa. As there are no tsetse flies in this hemisphere, the organism adapted to transmission by a different insect vector.
I’m too out of date to comment intelligently on the Bartonella, and have too many irons in the fire just now to brush up on it.
African trypanosomiasis, or “sleeping sickness,” is caused by a different species of trypanosome, Trypanosoma brucei, than Chagas’ disease, which is caused by T. cruzi. The vectors transmit the disease in quite different ways, tse-tse flies via saliva and reduviid bugs (the Chagas’ disease vector) via their feces.
Please provide a cite for your statement if you have one.
I don’t. I was basing it on what was believed/reported when I was in college. I took Parasitology in 1982.
I’ve skimmed and bookmarked the paper you provided, and will read it later. In the meantime, as I know you to be careful and correct in such matters, I surrender unconditionally. Thanks also to Tamerlane for the pdf; I’ve downloaded it (for some reason, I simply can’t read some pdfs online, but I can download them; it’s weird) for future reading.
And apologize to all for having posted incorrect information. :o :smack:
Since I’m unaware of the existence of trypanosomiasis in the Old World outside Africa, and we do know that S. America and Africa were once united, I assume that the New World trypanosomes must have been there for (I forget how many) million years since the two continents divided. Have fossils of tsetse flies been found in S. America? Do we know when they went extinct there? I recall that fossilized tsetse have been found in N. America, but were many millions of years old.
The trypanosomes must have adapted to the Reduviids, but when? Intermediate hosts? Parasit still fascinates me; doesn’t show much, does it?
I took Medical Entomology in the spring of 1986 and Parasitology in fall, 1987 - so I’m not really that much more up to date :).
In the article I cited they speculate that the Trypanosoma cruzi clade arose in the New World, post-split with Africa around ~100 million years BP, but sometime before the split with Australia, as a member of that group is apparently present as a parasite of kangaroos, while members in the Old World infects only very vagile bats. Based on that they speculate a truly ancient host-parasite relationship with the T. brucei group in Africa, perhaps co-evolving along with Glossina and very earliest hominids. This as opposed to a very recent T. cruzi clade relationship with humans, going back only a few tens of thousands of years and representing at base only a slight broadening of a widespread pre-existing suite of New World mammalian hosts, including primates.
Thanks also to Tamerlane for the pdf; I’ve downloaded it (for some reason, I simply can’t read some pdfs online, but I can download them; it’s weird) for future reading.
