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Dremmer
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Humans are the only mammal that drinks the milk of other mammals and the only mammal that drinks milk as adults. When did we start doing this?
ryan_m_b said:Being able to drink milk after young childhood is a phenomenon called lactase persistence and has evolved multiple times in human history. Lactase persistence is caused by a mutation in the LCT (lactase) gene, the first to be discovered and the most common amongst Europeans is the -13910*T SNP whereby a cytosine is exchanged for a thymine, this mutation occurs 13.9kb upstream and is almost ubiquitously found in European populations. Other SNPs include -14010*C (common in East Africans) and -13915*G (common in Middle Eastern/North Africans). The exact method by which each SNP confers lactase persistence is unknown however it is suspected that the overlap of SNPs and transcription factor binding sites are the cause. In the case of the -13910*C it has been shown that the Oct-1 transcription factor for lactase binds more strongly with a thymine in place of a cytosine.
Analysis of the LCT persistent gene has revealed that the sequence surrounding the gene has extensive homozygosity with diversity in this sequence is very low indicating that the genotype is advantageous and must have spread to such a high frequency recently. Attempts to date the -13910*T allele by examining microsatellite diversity date the mutation at somewhere between 7,400 and 12,000 years old. This is interesting because it coincides with the adoption of cattle farming in Europe, additionally analysis of ancient DNA shows that the allele is either not present or is at very low frequency before this time. -13915*G an SNP found in Arab genomes is dated at just 4000 years ago, 2000 years after the start of camel milk farming. It is difficult to say how lactase persistence is an advantageous allele. The calcium assimilation hypothesis that posits that in populations with insufficient sunlight lactase persistence makes up for vitamin D loss though this theory does not explain how African and Arab populations evolved LP. The nutritional hypothesis posits that the nutritional benefit gained from lactose is such an advantage on its own it is strongly selected for though there is no strong evidence of this.
Whilst the exact reason as to why LP is an advantage is not known it is safe to say that it is clearly an advantage to have been selected for at multiple times in history.
lisab said:Very interesting and informative.
Do you know if drinking milk introduced any new diseases to humans?
daveb said:There are some studies which suggest a possible link between milk and diabetes.
They aren't considered reliable or conclusive studies.daveb said:There are some studies which suggest a possible link between milk and diabetes.
Two recent prospective studies found no apparent association between development of antibodies to islet antigens and feeding patterns in high-risk infants with a first-degree type 1 diabetic relative.
Milk is pasteurized to kill pathogens in raw milk.lisab said:Very interesting and informative.
Do you know if drinking milk introduced any new diseases to humans?
Pasteurization kills pathogenic bacteria which occasionally may be present in milk, including those causing tuberculosis (Mycobacterium bovis), listeriosis (Listeria monocytogenes), Q fever (Coxiella burnetii), brucellosis (Brucella), campylobacteriosis (Campylobacter), salmonellosis (Salmonella), and several other foodborne illnesses (e.g., Escherichia coli O1577)
Evo said:Milk is pasteurized to kill pathogens in raw milk.
http://en.wikipedia.org/wiki/United_States_raw_milk_debate#Pasteurization
Probably because it seemed too obvious. lisab was probably also thinking of disease above and beyond these illnesses, but thought I'd post them anyway.ryan_m_b said:I was going to mention this but for some reason completely forgot to...
ryan_m_b said:Thankyou I don't know of any specific examples I guess but drinking milk would have increased the risk of catching disease from other animals.
Do you have any refs for this?
Evo said:Probably because it seemed too obvious. lisab was probably also thinking of disease above and beyond these illnesses, but thought I'd post them anyway.
That was from 1992 and said further studies should be ready in 5-10 years, so I looked for those newer studies and found the journal link from 1999.daveb said:Well, http://www.time.com/time/magazine/article/0,9171,976188,00.html" Time article references New England Journal of Medicine, which I don't have access to so can't verify it.
Oh no, I was just saying that the aticle says they weren't conclusive, not you.However, I said "suggest a possible link" - I never said they were conclusive Evo.
Proton Soup said:speaking of diseases, people used to (still?) get cowpox from milking cows.
http://en.wikipedia.org/wiki/Cowpox
but you could even consider that a sort of additional benefit.
wikipedia said:The virus is found in Europe, and mainly in the UK. Human cases today are very rare and most often contracted from domestic cats. The virus is not commonly found in cows; the reservoir hosts for the virus are woodland rodents, particularly voles. It is from these rodents that domestic cats contract the virus. Symptoms in cats include lesions on the face, neck, forelimbs, and paws, and less commonly upper respiratory tract infection.[7] Symptoms of infection with cowpox virus in humans are localized, pustular lesions generally found on the hands and limited to the site of introduction. The incubation period is nine to ten days. The virus is prevalent in late summer and autumn.
ryan_m_b said:Taken from that wiki page
You're right of course that this would be an advantage. Catching and dealing with cowpox was such a great advantage that it was one of the things that inspired Jenner to test inoculation.
The exact date when adult humans started drinking milk is uncertain, but it is believed to have occurred around 10,000 years ago during the Neolithic Revolution. This was when humans began domesticating animals for food and milk became a staple part of their diet.
Adult humans started drinking milk for its nutritional benefits. Milk is a rich source of calcium and protein, which are essential for bone health and muscle development. It also contains other important nutrients such as vitamin D, potassium, and magnesium.
No, the consumption of milk varied among different populations and cultures. Some populations, such as those in Europe and parts of Africa and Asia, developed lactase persistence, which allowed them to digest milk into adulthood. Other populations, such as those in East Asia and Native Americans, did not develop this trait and are more likely to be lactose intolerant.
It is believed that the consumption of milk by adult humans evolved through a process called natural selection. Those individuals who had the genetic mutation for lactase persistence were able to digest milk and derive its nutritional benefits. This gave them a survival advantage, allowing them to thrive and pass on their genes to future generations.
No, drinking milk is not necessary for adult humans to survive. In fact, many people around the world do not consume milk or are lactose intolerant. However, milk can be a valuable source of nutrients for those who can digest it and choose to include it in their diet.