29 Point of Origin
Evidently a movie was released over the summer which promoted the Paleo diet. I’m sure you will be shocked to learn that I didn’t see it. I did see the trailer for it, though. This is a screen capture from that trailer. As I understand it, this is Loren Cordain explaining to someone who knows less about nutrition than he that if we imagine a football field as a timeline representing all of human history, then the introduction of agriculture would be located on that field someplace within the one yard line. All the rest of the field represents the time before agriculture. He wants the viewer to see how much bigger the “Paleo zone” is than the tiny “agriculture zone”. If you’ve already seen my Ancestral Cholesterol videos, you know that I think that historic changes equally as important as the beginning of agriculture in our discussion of nutrition were the germ-theory-derived concepts of sanitation and the control of infectious disease, and those would have occurred even closer to the goal line where they are.
Since I haven’t seen the Paleo movie I am trusting this blogger’s description of that still. I think this write-up is probably accurate enough for my purposes because it is so similar to that passage we saw in Robb Wolf's book.
The premise here is all wrong. Our ancestors weren’t just dropped off by an alien spacecraft fully formed into Loren Cordain- and Robb Wolf-shaped organisms.
As with most concepts in evolutionary theory, Richard Dawkins beautifully explains why we can't fix in time a particular start to humanity. There was never a precise point of transition from our ancestral species to our current modern form. The transitions in evolution take place gradually. That football field could be more than 400 times longer if it were to go back to our beginnings as primates but even saying that misses the point. Dawkins quotes Darwin, who said, “In a series of forms graduating insensibly from some apelike creature to man as he now exists, it would be impossible to fix on any definite point when the term ‘man’ ought to be used.” There was never a particular point in time when we became anatomically modern humans. Scientists use their terminology to identify species or subspecies – like modern humans – and a time when they appeared, but this is just a convention to allow them and us to use labels and form ideas so we can talk to each other about organisms and their stages of evolution. Yes, anatomically modern humans were different than their ancestors, but we are also different from the modern humans of 10,000 years ago.
This is a graph of the total human population of the Earth over the last two million years. Notice that for most of that time, which goes back further than the Paleo football field, the human species was not really flourishing. You would expect that death rates more or less matched birth rates on average over this time. Once we hit that last portion of the last yard before the goal line, we see an enormous increase in human population. Now I know that Robb Wolf says he was a research biochemist but I think I need to get rather basic for him here.
If we were in the lab trying to influence the population dynamics of a colony of bacteria, and if we could induce an exponential growth phase, we might fairly conclude that we had chosen a successful growth medium. We would say that the bacteria did pretty well with the food we gave them.
Well, I think the explosion of the human population coinciding with agriculture suggests an improvement in the food supply for us as well. Don't overthink this analogy, by the way.
In fact we can look at that population explosion more closely and link increases in population growth with particular stages of the Agricultural Revolution. As you will notice, the introduction of agriculture was gradual. You might say our agricultural techniques evolved. Population growth accelerated more and more closer to our end zone than the points Wolf and Cordain picked. Biologically, this is what success looks like. Just compare the left and right sides of that graph. Isn't it amazing that there are fad diet promoters who think humans were fueled better on the left side?
Now just like with our bacterial colony, populations can't grow exponentially forever. I'll come back to this point in my Second-Guessing the First Farmers video.
A huge population explosion should be recognized as an indicator of the acquisition of an improved food supply, especially when it can be chronologically tied to changes in that food supply, but let me be clear: I do not think that this is how we should figure out what proper nutrition is. We have nutrition science for that. We don't expect anthropologists to figure out nutrition any more than we expect nutrition scientists to figure out anthropology, Robb Wolf's daydreams notwithstanding. But let's play the Paleo football field game anyway. Let's assume that everything just started 150- or 200,000 years ago. What do we know about that time period? Was it a carb-free environment, as imagined by the low-carb doctors?
First, let's get straight that anatomically modern humans were not in Europe at that time. Not even close. We modern humans had an African origin. I hope you knew that already.
For the sake of argument, let's say we humans came on the scene 150,000 years ago. Anatomically modern humans, hereafter simply called "humans" in this video, didn't even start to leave Africa for another 50,000 years.
Low-carbers imagine the first humans living in an Ice Age East Africa on the savannah hunting big game. There is support for all of that, but what if that isn't really the most accurate view of our history? What if something important has been forgotten in this narrative? If the Paleo promoters say that a particular diet made us human, doesn't it make sense to investigate what the place was like from which we humans first emerged?
We live now in an age of genetic research. It is possible for scientists to examine genetic material from living populations and infer the place where their forbears likely first took root. A key principle which underlies this type of research is that genetic diversity increases toward the point of origin of a species. As a species spreads out, population densities generally diminish and genes spread around less freely because there is more physical space between everyone. Using this idea, Sarah Tishkoff, Floyd Reed, and colleagues calculated that the main center of genetic activity at the dawn of humanity was not in East Africa, but rather southwestern Africa near present day Namibia and Angola.
This graphic appeared in the New York Times illustrating the concentration of diversity in this region.
This is the illustration the researchers created themselves for their paper. This is a different idea from what had been presumed in the past.
The reason it had been believed that humans came from East Africa or perhaps southern Africa was simply because that is where ancient human remains had been found. East Africa had large variations in climate that produced dry periods during which remains could be well preserved.
For this reason, even these same researchers believed in 2006 that modern humans originated in East Africa.
However, even then they said the lack of remains outside East and Southern Africa may only reflect the poor conditions for the preservation of remains in other areas. Moreover, the remains may have been found where they were because those were simply the places that had been investigated the most.
Rainforests are humid and warm, so their conditions would promote the decay of any human remains left there.
Archaeological research in tropical rainforests is in its infancy. Until enough excavations take place there and until more remains are found, we lack the physical evidence we need to date the first human activity there.
Until the research is done, we cannot assume that the rainforests were not populated.
In order to understand the implications of this newly inferred center of human genetic diversity, we should first recognize that it is advantageous to a species to have a high degree of genetic diversity. A high level of genetic possibilities will provide most of the genetic material that later generations will use to adapt to different environments as they enter new habitats.
Evolution can happen more rapidly where genetic diversity is greatest. With less genetic diversity, there is slower adaptation.
All of this would have applied to humans just as any other organism.
You will recall from my Ancestral Cholesterol videos that some of our most ancient populations are situated near the geographic center of diversity that Tishkoff identified. If we are in the mood to speculate, it seems reasonable to say that their cholesterol levels have the best chance of being representative of cholesterol levels at the beginning of our football field.
I don't think Tishkoff and Reed would be impressed with the Paleo football field. They wrote, "The transition to modern humans was unlikely to be sudden." They said that traits were acquired in the lead-up to this stage "over a substantial period of time and across a broad geographic range within Africa."
If we accept that humanity began in Africa, we must also accept that most of our evolutionary development took place under the conditions there. African populations by and large have the highest genetic diversity among living humans.
Moving away from Africa, genetic diversity is much less. Therefore the random mechanism of genetic drift becomes much more of an influence upon mutations fixed outside of Africa. Traits acquired outside Africa are more likely to have been the product of chance rather than positive selection.
This is especially important for us to consider since the human populations that left Africa were very few in number. There was a genetic bottleneck that may have limited the first colonizers to as few as only 600 founding females. I think this greatly limits any claims that might be made about how well adapted we are to any conditions encountered outside of Africa. Of course, minor adaptations happened, such as the lightening of skin color. However, there were probably never any significant alterations to our major systems, like our digestive system.
So what would the time and place of our greatest historical genetic diversity have been like? What can we guess about that environment that might allow for a more accurate, although still misguided, real Paleo diet?
As I said in past videos, humans inhabited refugia – isolated pockets of warmth and vegetation – during the Last Glacial Maximum. They would have migrated to environments where they could thrive rather than suffer through environments that might have risked their extinction. I think we are well justified if we apply the refugia hypothesis for all previous time periods as well. Humans, like any other animals, would have found places to carry on where they were buffered from extreme climates that they could not manage. Can you imagine yourself surviving in a cold dry landscape year after year after year? Can you imagine doing so before the control of fire? Can you imagine raising a family in such a place? Humans outside the refugia would likely have simply died off.
This map shows the calculated distribution of microclimate refugia during the worst of the Last Glacial Maximum. Refugia are here defined as areas with at least 75% forest cover with a canopy height of 22 meters. This climate simulation does not extend as far back as the point of origination of anatomically modern humans, but the fact that substantial refugia remained in the general area in which the genetic evidence tells us that we were born - even during the Last Glacial Maximum - should cause us to consider that our first modern ancestors called the rainforest their home, and not the dry grasslands as is commonly believed.
You can see that the distribution of vegetation during the Last Glacial Maximum was not radically different from what existed in the pre-industrial world. There would certainly have been areas covered in rainforest.
The best graphical material I have found to help you see that rainforests would have persisted in West Africa back to the time of the first anatomically modern humans are these reconstructions based on pollens found in sediment cores. These images represent vegetation as far back as 150,000 years. This suggests that there would have existed warm and wet regions which may have hosted the development of anatomically modern humans.
Tropical rainforests most likely would have persisted straight through the Ice Age.
There have been archaeological discoveries in rainforests that suggest that ancient humans did inhabit them.
Ancient stone tools have been found in areas presently covered by rainforest.
This paper reports on the many forested sites in which remains have been found.
Apparently some have argued that early humans could not have occupied tropical rainforests because adequate food could not have been found there. For Mitsuo Ichikawa, the key to assessing the validity of this claim was to ascertain the supply of wild yams in the rainforest. Would there have been enough yams there year-round to supply humans with adequate food?
He was writing in that paper about equatorial West Africa, in this case the Congo Basin, so his research is quite applicable to our discussion of the earliest humans.
One of his former students spent time with Pygmies who showed him that they were able to collect all the yams they needed, even during the dry season. Adequate food does exist in the rainforest to support primitive populations.
Other authors have concurred that the rainforest supplied enough tubers to the support the Africans of deep history.
As humans left Africa and dispersed into Europe, they most certainly would have been confined to localities with tolerable temperatures and adequate vegetation.
It's true, they found ways to colonize even inhospitable surroundings over time, even places as unlikely as the Arctic.
However, as these populations occupied these areas one by one, they would have become increasingly genetically isolated.
The same can now be said of the low-carb hunter gatherer populations. They have been limited in their population growth by their limited resources. At the population level, they have not thrived.
We only need to look at a map of the locations of recent hunter gatherer cultures to see that they were far removed from one another and mostly far removed from Africa. They all went off on separate tracks, and as a consequence, their unique genetic attributes are not shared with us. This is not to say they are so different, either. Just like us, they are fundamentally African, too.
A Paleo article of faith is that meat made our brains bigger, simple as that. I will reexamine this claim with fresh material in the next video.