Skip to comments.Early Cities Spurred Evolution of Immune System? [ "Amazing" DNA results show benefits ]
Posted on 11/12/2010 9:03:42 PM PST by SunkenCiv
As in cities today, the earliest towns helped expose their inhabitants to inordinate opportunities for infection -- and today their descendants are stronger for it, a new study says.
"If cities increase the amount of disease people are exposed to, shouldn't they also, over time, make them natural places for disease resistance to evolve?" asked study co-author Mark Thomas, a biologist at University College London... study co-author Ian Barnes, a molecular paleobiologist at University College London, screened DNA samples from 17 groups long associated with particular regions of Europe, Asia, and Africa -- for example Anatolian Turks and the southern Sudanese.
Barnes analyzed the DNA samples for a gene associated with resistance to tuberculosis (TB) and suspected of being associated with resistance to leprosy as well as to leishmaniasis, a reaction to sand fly bites, and to Kawasaki disease, a childhood ailment that involves inflamed blood vessels and can lead to heart disease...
In areas of ancient urbanization, it turned out, "we found very high frequency" for the TB-resistance gene, study co-author Thomas said. But, for example, "the Saami people from northern Scandinavia and the Malawi people from Africa, who have little history of urban living, did not have this frequency.
...said epidemiologist Andrew Read... "That it took the rise of disease-ridden cities to cause this resistant gene to become common suggests to me that there must be a cost to having it -- or else it would have been common in the first place," said Read, of Pennsylvania State University, who wasn't involved in the new study... And while it may be small consolation to the allergic and arthritic, having those disorders, Read said, might be a small price to pay for avoiding death by tuberculosis.
(Excerpt) Read more at news.nationalgeographic.com ...
Workers excavate a culvert at the circa-2725 B.C. site of the Harappa settlement in Pakistan (file photo; Photograph by Randy Olson, National Geographic)
· join list or digest · view topics · view or post blog · bookmark · post a topic · subscribe ·
Bronze Age Forum
Excerpt, or Link only?
· Science topic · science keyword · Books/Literature topic · pages keyword ·
People are similar to bacteria in one sense, i.e. there are always a few in any population who are naturally immune to certain things, therefore they don’t really “evolve”. It is just the naturally disease resistant people who propagate.
So... we are the result of our environment.
I disagree with this thesis.
Most communicable diseases to which humans are susceptable are contracted from domesticated animals. Hence areas of the world where domesticated animals weren’t the norm before the arrival of Europeans, such as the Western Hemisphere, were horrifically affected by diseases like small pox, which originated from close contact with cattle.
It’s adaptation, not evolution.
“The corbeled arch is made of overlapping courses of stones, each block projecting slightly further over the opening than the block beneath. The weight of the blocks above the supported end of the the projecting blocks help prevent the unsupported ends from tipping and falling...”
From Abacus to Zeus, by James Smith Pierce, Prentice-Hall, Inc., 1968.
While caring for my husband who eventually died from Alzheimers I noticed that he was most likely to escape from the house as I was quickly trying to get dinner cooked for him. I then though of those stories of American Indian elderly wandering off into the forest in the middle of winter to die so their grandchildren would have more food.
Anyway, I have developed a theory that Alzheimer’s is actually a positive genetic survival gene. Among tribal and spread out populations, if there was a tendancy to wander off in search of food while failing from Alzheimer’s ones descendents probably stood a better chance of surviving because more food was available. This behavior on my husband’s part was about a year before he became too debilitated to be useful around the house/camp. Thus, had we been a primative encampment, he would have gone out to pee and look for food, and never found his way back just before he would have become a general burden to the tribe.
Genetically, my husband was Scottish, with some American Indian, red haired, reddish sun sensitive skin, heavy boned, pale blue eyes, very hairy, warrior temperment, and I suspect more of the Neanderthal genes than most.
Bookmarking this due to interest in Alzheimer’s stories....
Your observation is very interesting.
There is some confusion about the term evolution. While Darwin proposed the phenomenon, it was not until Gregor Mendel did is work along with others that the principles of genetics were established. Darwin new that more useful traits became the dominant ones over time amoung species. He did not know anything about dominant and recessive genes, nor about mutations. Adaptation in the biological sense is the building up of a reservoir of favorable genes among a population. In the social sense, it is learning to change one’s behavior to function better in difficult circumstances.
Thus, the white skin mutation in African homo sapiens as it became more common enabled our ancestors to push the Neanderthals out of Europe. This was a genetic adaptation, or evolution.
On the other hand, when Greenland became much colder in the Middle Ages as a result of The Little Ice Age, the residents failed to learn and adopt the living and hunting strategies of the Inuit natives and their settlements died out. This was a failure of social adaptation.
Interesting theory. Alzheimer’s almost always strikes the elderly well past child bearing and effective working age. However, in primitive societies the elderly perform the critical task of childcare and food preparation while the parents are out hunting/gathering/growing food and Alzheimer’s doesn’t affect everyone or even most people. I don’t know if it is more prevalent among some races than others. Do you?
99.9%of people before the year 1850 didn’t live long enough to get it. we’re talking dead at 55 in the middle ages for sure, 30 for bronze age people.
My husband was able to help me build a cabin with no available electricity. We did this from 2002 to late 2004. He died in June 2005 at age 75. He could not plan anything, but if I began a saw cut, I could turn over the sawing to him. He could hold a timber in place while I hammered it. He loved to sweep the leaves off the moss and in the city the sidewalk. He simply could not remember anything for more than 10 or 15 seconds. Thus he could do any job that was a series of continuous actions. Before he became seriously nonfunctionally, I had to call the police because he had swept 10 blocks of sidewalk, just kept on going and I had no idea where. Always before, he would sweep to the end of the block then come back to the house. After that I had to watch him. This was also the time period when he would wander off if he was hungry. In a primative society with people all around it would be easier for an Alzheimer person to function usefully. In a primative society, he could have gone out with others and picked berries or nuts and carried them home. He could have played with children under supervision. He could have turned a spit.
I checked a little about frequency of Alzheimers in foreign urban populations. A long settled area of India had a very low rate. A long settled urban area in Africa also had a very low rate. Black population in Cleveland, Ohio had a high rate. In conjunction with my theory I think that American blacks would have been captured from the jungle and small scattered villages, and not from the large urban centers, which fits with my theory. Obviously, this could be studied a great deal more, especially as specific genes related to Alzheimers are discovered.
Ran across some interesting stats from the early modern period (1500s). They were about the marriages of peasants in Central Germany.
The average age of marriage for a male was 30 years old. This was because a guy generally couldn't marry till he inherited the farm. This implies his father, who himself got married around 30, was living on average well into his 60s.
The very low numbers tossed around for average life expectancy are generally skewed drastically by child mortality. If every adult lives to 60 and you have 50% child mortality, you have "average life expectancy" of 30 years.
True, though this dates from before 1700 BC, so the architectural flaws are understandable :)
Your theory has a lot of truth behind it — have you pursued it any further? A white paper sounds possible
not good — that pic is originally from Stormfront. Not relevant to this article
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.