In his book “The Borderlands of Science” Micheal Shermer wrote about how the hunting and collecting people of the Paleolithic age were taller, healthier and bigger boned than people who abandoned foraging to become farmers. The average height of hunting and collecting people was 5’10 for men and 5’6 for women. After farming became established heights dropped to 5’3 for men and 5 1’ for women. Since when was food more important than genes and the “variation, selection, transmission” process of evolution? Is this a strong argument for nuture over nature? I don’t believe it is and I’m pretty sure the change in heights has more to do with “genetic variability” whereby potential is either fulfilled or it’s not. Is that right? If so, how much is known about potential in human beings? Is potential limited or limitless? How easily can it be influenced?
There’s at least three possibilities: First, the hunters and the farmers had essentially the same genes, but due to differences in nutrition, grew to different sizes. This is not in the least surprising, since it’s been seen numerous times in the past century: This is the reason that children of immigrants so often outgrow both their parents. Note, by the way, that this would have no effect on the genes; if Big Joe Hunter went and settled down on a patch of farmland, his son the farmer would be of typical farmer height, and vice versa.
The second possibility is that being big is somehow advantageous to hunters/foragers, and being small is likewise advantageous to farmers. The two groups separated, and the tall hunters and short farmers were more sucessful, so after some long span of time, the hunters had mostly tall genes and the farmers had mostly short genes.
The third possibility, of course, is that Michael Shermer is just wrong. I don’t know what his qualifications are, and he’s probably not, but it’s a possibility that must be kept in mind.
Since when was food more important that genes and the “variation, selection, transmission” process of evolution you ask? Well, since always. If your organism doesn’t have adequate nutrition or resources to acheive it’s potential (or even survive), then it doesn’t matter that it could have had an advantage; it starved to death and never entered the picture. Most animals in the wild get by on what they find… very few live in optimal conditions where every need is met. So when they do come across good fortune say in the form of a good diet, they can use those resources to come closer to their genetic potential, even though that hasn’t changed. Look at the bears on the coasts (where there’s more berries and salmon) and compare the size to bears 500 miles inland.
Phenotypic potential is not either translated from the genotype 100% or the creature dies. You can influence the growth pattern of an organism in all kinds of ways. My cat was very sick as a kitten, which stunted her growth; she is now 12 years old and weighs 4 pounds, but I’m pretty sure she wasn’t programmed to be that small. Break your legs every 6 months, they won’t grow quite normally. Nutrition is very important for young people, and can really influence how well they grow.
From what I’ve heard, it seems that once we started eating the same couple things from the same place all the time year after year, we started going short on certain nutrients that used to come in from a well-traveled and varied diet. Since anyone could be a farmer, that is, it doesn’t take a certain body type, the genetics probably stayed about the same and most people were stumpy because they didn’t eat very well(in the sense of balanced nutrition) compared to before they settled down. I’d say the genes for 6-footers were always around, just not very “well fed” so to speak. Otherwise, where did that race of big hunter-gatherers come from that gave rise to all the tall people over the past 50 years and when did the supposedly genetically tiney farmers become extinct?
Long legs must be better for walking long distances, that may be a reason for the height of nomadic people and would amount to an environmental adaptation. Farmers may require shorter, stronger bodies. I had assumed that food was the issue but may be Michael Shermer didn’t intend that. The size of the coastal bears compared to the inland bears is very interesting though. I’ve often thought that something must surely come out of the fact that a great many human beings today have better nutrition, hygiene and physical comfort than at any time in history. However, although it’s easy to see how that helps a person fulfil their genetic potential in their own lifetime I can’t quite understand how they could transmit the ability to achieve potential through their genes. Am I making sense? Possibly. Evolutionary theory! Fun for all the family! Not as difficult as your average theory.
They don’t need to transmit the ability to achieve potential through their genes. A hunter/gatherer diet was more complete, higher in protein, put less stress on the body in collecting, didn’t require children to work and a whole range of other factors that agricultural diets haven’t been able to achieve until quite recently. Hunter gatherers were nomadic and moved away from their own faecal contmination regularly and lived at low population densities so much disease was rare. Farmers were necessarily sedenatry, located near water sources that became permanantly contamianted with faeces, had rats, mice etc. living wiht them permanantly. Childhood disease was chronic. This was ongoing. It didn’t just happen for the first generation of farmers.
The children of the first farmers were stunted because they were working the fields from the age of ten and living on a diet consisting 80% of carbohydrate, as opposed to the 50% protein diet of hunter gatherers and ill a significant portion of their lives. They never achieved their genetic potential. They grew up and had children who were also overworked, dieased and malnourished, as a result of which they too were stunted and never reached genetic height potential. Their children were subjected to the same stresses and so on. At any stage you could have taken those children at birth placed them in a hunter/gatherer tribe and they would have grown to be 5’10". The genetic potential hadn’t changed, it just never got realised in any agricultural population at any time.
What leads you to concude that Shermer didn’t intend to attribute this to the fairly obvious dietary differences between the groups? And if he didn’t what exactly did he attribute the height changes to? The dietary differences alone can more than account for the differneces in height without even taking into account the social and epidemiological changes associated with the change in lifestyle. There is certainly no need to suggest any evolutionary change has occured although it is possible, as Chronos noted, and that too wouldn’t conflict in any way with evolutionary theory as accepted for the last 80 yaers or so.
Social Darwinism and genetic variability are not exactly compatible ideas are they?
Gaspode: I just assumed, I suppose, that a change in height would be seen as evolutionary rather than as a result of bad nutrition. The fittest survive and in a change from hunting and collecting to farming that means people with farming-friendly anatomy.
Soacial Darwinism, such as it is, should have no problem with genetic diversity AFAIK. If a SD theory stalls because of genetic diversity the theory is fundamentally flawed.
The change in height could be evolutionary of course, but the evidence in the form of rapid height increase when populations changed diet, gained access to better health care etc. means that there is no need for any evolutionary change. Since height differences can be explained by environmental diferences anyone proposing a genetic cause would need to provide some evidence, which in this case is going to be nearly impossible.
The other problem is that I can’t think of a hunter/getherer or agricultural phenotype. The Khoisan are hunter/gatherers while various South American Indian groups are agriculturalists. Both are short, fairly slight people. The American Indians are agricultural and most groups are fairly similar phenotypically to Australian Aborigines. The tallest groups of people on Earth are various African people who are almost entirely dependant on animal agriculture, while Eskimos are classic hunter/gatherers and are fairly short. I really can’t imagine why farmers would need to be taller or shorter than hunter/gatherers.
IANABiologist, but think of your genes as construction plans. The genes call for building materials, the amino acids, to make proteins out of which your bones, muscle, etc., are made. If you haven’t gotten enough protein in your diet such that you’ve got fewer than the desired number of amino acids, your building is not going to be as tall as the plans call for, no matter how much this annoys the architect.
–Cliffy
Thank you to everybody here who replied. The posts are so informative and, as I understand it, refreshingly nuture rather than nature oriented.
That’s what Lysenko thought (“The belief in the inheritability of acquired characteristics”). And through manipulation of Stalin he managed to convince an entire generation of Sovjet biologists in the stalinistic era.
It’s a classic example of how politics can influence science.
(Food for thought when politicians talk about ‘creationism’)