Category Archives: Evolution

John Hawks’ Perspective on the New Dmanisi Skull

…at his blog. A snippet:

What population structure characterized the African ancestors of the Dmanisi hominins? If we look to the MSA African model, the structure would be one of multiple populations, strongly differentiated, that had existed for hundreds of thousands of years. They may have had adaptations to local ecological conditions, but they were not isolated — they shared genes and one might occasionally replace another, only to re-differentiate as climate fluctuated. The African populations that existed at 1.8 million years ago were probably a modified subset of those that existed 2 million or 2.2 million years ago. Some of these populations would have been morphologically distinctive enough that paleontologists might call them different species. Some of the remixture between them would have been slight, on the scale of Neandertal mixture into today’s human populations. But those cases were at one end of a continuum that included larger amounts of genetic exchange and more rapid turnover. It was a braided stream, in which some of the rivulets were long, but others were short.

Read the rest and you’ll find a brief review of early human evolution.

Human Longevity Blossomed 30,000 Years Ago

…long before the Agricultural Revolution according to Rachel Helmuth writing at Slate.

Throughout hominid history, it was exceedingly rare for individuals to live more than 30 years. Paleoanthropologists can examine teeth to estimate how old a hominid was when it died, based on which teeth are erupted, how worn down they are, and the amount of a tissue called dentin. Anthropologist Rachel Caspari of Central Michigan University used teeth to identify the ratio of old to young people in Australopithecenes from 3 million to 1.5 million years ago, early Homo species from 2 million to 500,000 years ago, and Neanderthals from 130,000 years ago. Old people—old here means older than 30 (sorry)—were a vanishingly small part of the population. When she looked at modern humans from the Upper Paleolithic, about 30,000 years ago, though, she found the ratio reversed—there were twice as many adults who died after age 30 as those who died young.

The Upper Paleolithic is also when modern humans really started flourishing. That’s one of the times the population boomed and humans created complex art, used symbols, and colonized even inhospitable environments. (The modern humans she studied lived in Europe during some of the bitterest millennia of the last Ice Age.) Caspari says it wasn’t a biological change that allowed people to start living reliably to their 30s and beyond. (When she looked at other populations of Neanderthals and Homo sapiens that lived in the same place and time, the two different species had similar proportions of old people, suggesting the change was not genetic.) Instead, it was culture. Something about how people were living made it possible to survive into old age, maybe the way they found or stored food or built shelters, who knows. That’s all lost—pretty much all we have of them is teeth—but once humans found a way to keep old people around, everything changed.

Read the whole enchilada.

Adam Lived 340,000 Years Ago

African Savanna

African Savanna

…according to a headline at NewScientist.  That’s a tad off the 6,000 years or so suggested by some Bible scholars.  You’ll enjoy this article if you’re interested in human evolution.

Africa is said to be the cradle of humanity, but the exact coordinates of the nursery are unknown.

When you read of the Y chromosome below, remember that only men have them.  Women have two X chromosomes; men have one Y and one X.  Sounding familiar?

Some snippets from the article:

Hundreds of thousands of people have now had their DNA tested. The data from these tests had shown that all men gained their Y chromosome from a common male ancestor. This genetic “Adam” lived between 60,000 and 140,000 years ago.

Scientists analyzed the DNA of Albert Perry, and African-American who recently died in South Carolina.

Michael Hammer, a geneticist at the University of Arizona in Tucson, heard about Perry’s unusual Y chromosome and did some further testing. His team’s research revealed something extraordinary: Perry did not descend from the genetic Adam. In fact, his Y chromosome was so distinct that his male lineage probably separated from all others about 338,000 years ago.

The first anatomically modern human fossils date back only 195,000 years, so Perry’s Y chromosome lineage split from the rest of humanity long before our species appeared.

What are the implications? One possibility is that Perry’s Y chromosome may have been inherited from an archaic human population that has since gone extinct. If that’s the case, then some time within the last 195,000 years, anatomically modern humans interbred with an ancient African human.

Read the rest.

Notable Quotes From Kuipers’ “Multidisciplinary Reconstruction of Palaeolithic Nutrition”

Australian Aborigine in Swamp Darwin

I scored of copy of “A multidisciplinary reconstruction of Palaeolithic nutrition that holds promise for the prevention and treatment of diseases of civilisation” by RS Kuipers, JCA Joordens, and FAJ Muskiet. I’m not going to review it here. I’m just assembling some interesting “facts” for my files, so this could be boring. You won’t offend me much if you stop reading now.

This paper is from the University Medical Center Groningen and Human Origins Group (Faculty of Archaeology, Leiden University), both in The Netherlands. It’s 23 pages long, not counting the 450 references.

I’ll following the spelling conventions of the paper’s publisher.

Introduction

“…our genome has remained basically unchanged since the beginning of the Palaeolithic era.”

“Since the onset of the Agricultural Revolution, some 10 thousand years ago, and notably in the last 200 years following the start of the Industrial Revolution, humans have markedly changed their dietary habits. Consequently, it has been advocated that the current pandemic of diseases of civilization results in part from the mismatch between the current diet and our Palaeolithic genome.”

These are some of the diseases that may result from the mismatch of our Palaeolithic genome and modern lifestyle (including diet): type 2 diabetes, high blood pressure, osteoporosis, fertility problems (polycystic ovary syndrome), pregnancy complications (pre-eclampsia, gestational diabetes), some cancers (colon, breast, prostate), heart disease (such as coronary artery disease), major and postpartum depression, autism, schizophrenia, some neurodegenerative diseases (Parkinsons disease, Alzheimer’s disease). [Sorry, Dr. Cordain – no mention of acne. And I wonder about dental and eye problems.]

Evolutionary Medicine

“Many, if not all, diseases can become explained [sic] by both proximate and ultimate explanations. The science searching for the late explanations has become known as ‘evolutionary medicine.’ Unfortunately, modern medicine deals mostly with proximate explanations, while ultimate explanations seem more prudent targets for long-time disease prevention.”

The term “evolutionary medicine” was coined by Randolph M. Nesse and George C. Williams in the early 1990s. It’s also called Darwinian medicine.

“…about 20% of modern hunter-gatherers reach at least the age of 60 years.”

After the transition to the Agricultural Revolution about 10,000 years ago, life expectancy fell from about 40 years to about 20 years. This is astounding news to me, assuming it’s accurate.  (Remember that for most of human existence, infant and child mortality has been very high. If an infant dies at 6 months old and an adult dies at 40 years, average life expectancy for the two would be about 20 years.)

Average life expectancy among modern hunter-gatherers is about 40 years—same as it was for students of the Harvard College class born in 1880.

Life expectancy in the Neolithic era was stable until the late 18th century, rarely exceeding 25 years in civilized nations.  At that point, life expectancy started to improve dramatically thanks to sanitation, water and food hygiene, immunizations, and quarantine practices. (Thomas Jefferson was the third president of the U.S.  His wife Martha had six children but only two survived to adulthood.)

The earliest species in the genus Homo appeared about  two million years ago.   Homo sapiens appeared about 200,000 years ago in south or east Africa. Several different hominin lines co-existed with modern humans.

The current world population of humans may be derived for only 1000 or so individuals that survived a decimating event.

The ability to store fat is one of the things that differentiate us from other primates.

Hunting and Our Ancient Diet

The composition of the early human diet is still hotly debated.

Lotta work to snag one of these

In modern hunter-gatherers, only about 30% of diet energy is derived from hunting, with the rest coming from gathering plant food and aquatic animals.

In contrast to the arid, hot, iconic savanna, “…the combined evidence strongly suggests that early hominins frequented the land-water ecosystem and thus lived there.” If rainfall and other conditions allowed, there would be wooded grasslands.

“…the proportion of the human gut dominated by the small intestine (>56%) suggests adaptation to a diet that is highly digestible, indicating a closer structural analogy with carnivores than to [animals that eat leaves and fruit].”

“The data of combined studies of early hominins and the more recent hominins suggest a gradual increase in dietary animal protein, a part of which may derive from aquatic resources. In the more recent human ancestors, a substantial part of the dietary protein was irrefutably derived from marine resources, and this habit was only abandoned in some cases after the introduction of agriculture at the onset of the Neolithic.”

Sea levels have risen over the past 17,000 years, up to 150 meters.

“In conclusion, there is ample archeological evidence for a shift from the consumption of plant towards animal foods.”

“For a long time period in hominin evolution, hominins derived large amounts of energy from (terrestrial and aquatic) animal fat and protein. This habit became reversed only by the onset of the Neolithic Revolution in the Middle East starting about 10,000 years ago.”

“The Homo genus has been on earth for at least 2.4 million years and for over 99% of this period has lived as hunter-gatherers.”

“We conclude that gathering plays, and most likely always played, the major role in food procurement of humans. Although hunting doubtlessly leaves the most prominent signature in the archaeological record, gathering of vegetables and the collection of animal, notably aquatic, resources (regardless of whether their collection is considered as either hunting or gathering), seems much easier compared with hunting on the hot and arid savanna. We suggest that it seems fair to consider these types of foods as an important part of the human diet, unless proven otherwise. Conversely, while hunting might have played a much more important role at higher latitudes, dietary resources in these ecosystems are rich in n-3-fatty acids (for example, fatty fish and large aquatic mammals), while the hominin invasion of these biomes occurred only after the development of more developed hunting skills.”

Even though traditional Maasai showed extensive atherosclerosis with fibrous changes and lipid infiltration, they had very few complicated arterial lesions and rarely had clinical cardiovascular disease events.

The Agricultural and Industrial Revolutions

“Contrary to earlier belief, the advent of agriculture coincided with an overall decline in nutrition and general health, but at the same time provided an evolutionary advantage since it increased birth rates and thereby promoted net population growth.”  [Both supporting references are from CS Larsen.]

Good news for birth rates

With the advent of the Industrial Revolution, nutritional quality and general health declined even more rapidly.

“Among the many dietary and lifestyle changes are: a grossly decreased n-3:n-6 fatty acid ratio, the combined high intakes of saturated fatty acids and carbohydrates, the introduction of industrially produced trans-fatty acids, reduced intakes of n-3 and n-6 long-chain polyunsaturated fatty acids, reduced exposure to sunlight, low intakes of vitamins D and K, disbalanced anti-oxidant status and high intakes of carbohydrates with high glycaemic indices and loads, such as sucrose and industrially produced high-fructose maize syrup.”  [Aren’t we eating more n-6 fatty acids, not less?]

Potential Benefits of a Palaeolithic Diet

The authors conclude with a review of the few medical scientific studies of Palaeolithic diets in modern humans. These are the ones by Frassetto, Osterdahl, Jönsson, and Lindeberg. I’ve already reviewed those here.  They missed O’Dea and Kerin’s study.

My Overall Impressions

This article seems very well researched.  It lays out a logical framework for the discipline of evolutionary medicine and should spur further clinical research.  It’s well worth a read if you have more than a passing interest in paleo lifestyle theory.

Bear in mind I’m not a paleontologist, anthropologist, paleo-anthropologist, or archeologist.  So caveat lector.

Steve Parker, M.D.  (B.S. degree in zoology)

Reference: Kuipers,RS; Joordens, JCA; and Muskiet, FAJ. A multidisciplinary reconstitution of Palaeolithic nutrition that holds promise for the prevention and treatment of diseases of civilization. Nutrition Research Reviews, 25 (2012): 96-129.  doi: 10.1017/S0954422412000017

PS: The Paleolithic diet is also called paleo, ancestral, hunter-gatherer, Stone Age,  Old Stone Age, and caveman diet.

Is Evolutionary Medicine a Valid Concept?

Not Harriett Hall, M.D.

Dr. Harriett Hall over at Science-Based Medicine has written a couple reviews of “evolutionary medicine” books.

Of the 2009 book, Dr. Hall writes:

Seeing everything in medicine through evolutionary glasses impresses me as more of a gimmick than as a clinically useful approach. Evolution clearly informs medical practice, but I can’t see the value of “evolutionary medicine” as a separate discipline and I can’t recommend this book.

 Her conclusion about the 1994 book:
I’m sorry, but I just don’t “get it.” Am I missing something? Am I just a contrary curmudgeon? Evolution is already an essential part of all science. Medical scientists already understand evolution and apply its principles appropriately. I didn’t see a single example in their book of any significant practical development in medical care that would not have occurred in the general course of medical science as it is commonly practiced, without any need for a separate discipline of “Darwinian medicine.” Evolutionary explanations, whether true or speculative, may satisfy our wish to understand “why,” but I can’t see that they have much objective usefulness.  Instead, they have produced at least one major annoyance: a movement that preaches to us how we ought to revert to the supposed diet of our ancestors (the Cave Man Diet, etc.).
My sense at this point is that evolutionary concepts do have a place in modern medicine, a role that has not been adequately explored and exploited.

Alex Hutchinson on the Paleo Lifestyle

Fleas from rats spread Yersinia pestis to humans

Alex Hutchinson has a recent article in Canada’s The Globe and Mail on the potential health benefits of the paleo lifestyle.  His conclusion:

So will going paleo really pay off with better health? As a big-picture guide to how to organize your life, definitely. But don’t get carried away with trying to recreate the exact details of a long-lost diet. Humans have changed and diversified even over the past few thousand years, so the only way to know what works best for your genes is to experiment. Go wild.

The article mentions the “increasing pace of human evolution,” an idea I’m still not convinced is valid.  Sure, a large population of critters should produce more genetic variation and mutation.  But it could take longer for a successful variation to spread through that population, compared to a smaller population.  It depends on selection pressure, to some extent.  The Black Plague in 14th century Europe changed that population quicker than any single genetic mutation I know of.  It wiped out 40% of the population.  Were those who survived genetically different from those who died?

I have much respect for Alex’s thoughts on exercise.  He usually puts more research and thought into his writing.  Check out his Sweat Science blog.

Steve Parker, M.D.