Home | Category: First Modern Humans (400,000-20,000 Years Ago)
POPULATION TRENDS BEGINNING ABOUT 100,000 YEARS AGO
100,000 Years Ago: Michael Balter wrote in Discover: Artistic Behavior Appears: Most researchers date the origins of Homo sapiens to between 200,000 and 160,000 years ago in Africa. Yet for their first 100,000 years, modern humans behaved like their more archaic ancestors, producing simple stone tools and showing few signs of the artistic sparks that would come to characterize human behavior. Scientists have long argued about this gap between when humans started looking modern and when they began acting modern. University College London archaeologist Stephen Shennan has proposed that cultural innovations were likely due to increased contact among humans as they began living in ever-larger groups. Shennan adapted Henrich’s Tasmanian model to much earlier human populations. When he plugged in estimates of prehistoric population sizes and densities, he found that the ideal demographic conditions for advancement began in Africa 100,000 years ago—just when signs of modern behavior first emerge.” [Source: Michael Balter, Discover October 18, 2012]
65,000 “Years Ago: Stone Tools Spread: Population size could explain why the same stone tool innovations show up at the same time across wide geographic regions. Lyn Wadley, an archaeologist at the University of the Witwatersrand in Johannesburg, has worked at the Middle Stone Age site of Sibudu in South Africa, where she found evidence of two sophisticated tool traditions dating to 71,000–72,000 years ago and 60,000–65,000 years ago. Similar tools pop up all across southern Africa at around the same time. Wadley says early humans did not have to migrate long distances for this kind of cultural transmission to take place. Instead, increasing population densities in Africa may have made it easier for people to keep in contact with neighboring groups, possibly to exchange mating partners. Such meetings would have exchanged ideas as well as genes, thus setting off a chain reaction of innovation across the continent.”
45,000 Years Ago: “Homo Sapiens Takes Europe: A bigger population may have helped H. sapiens eliminate its chief rival for domination of the planet: the Neanderthals. When modern humans began moving into Europe about 45,000 years ago, the Neanderthals had already been there for at least 100,000 years. But by 35,000 years ago, the Neanderthals were extinct. Last year Cambridge University archaeologist Paul Mellars analyzed modern human and Neanderthal sites in southern France. Looking at indicators of population size and density (such as the number of stone tools, animal remains, and total number of sites), he concluded that modern humans—who may have had a population of only a few thousand when they first arrived on the continent—came to outnumber the Neanderthals by a factor of ten to one. Numerical supremacy must have been an overwhelming factor that allowed modern humans to outcompete their larger rivals.”
25,000 Years Ago: “Ice Age Exerts A Toll: By 35,000 years ago, H. sapiens appears to have had the planet to itself, with the possible exception of an isolated population of H. floresiensis—the “hobbit” people of Southeast Asia—and another newly discovered hominin species in China. But according to work led by University of Auckland anthropologist Quentin Atkinson, human population growth, at least outside of Africa, began to slow down around then, possibly due to the climate changes associated with a new ice age. In Europe, total human numbers may actually have declined as glaciers began to cover much of the northern part of the continent and humans retreated farther south. But population levels never dropped enough for humans to start losing their technological and symbolic innovations. When the Ice Age ended, about 15,000 years ago, population began to climb again, setting the stage for a major turning point in human evolution.”
11,000 Years Ago: “Farming Sparks a Boom: Farming villages first appeared in the Near East during the Neolithic period, about 11,000 years ago, and soon afterwards in many other parts of the world. They marked the beginning of a transition from the nomadic hunting and gathering lifestyle to a settled existence based on cultivating plants and herding animals. That transition helped catapult the world’s population from perhaps 6 million on the eve of the invention of agriculture to 7 billion today. Archaeologist Jean-Pierre Bocquet-Appel has surveyed cemeteries across Europe associated with early settlements and found that with the advent of farming came an increase in the skeletons of juveniles. Bocquet-Appel argues this is a sign of increased female fertility caused by a decrease in the interval between births, which probably resulted from both the new sedentary life and higher-calorie diets. This period marks the most fundamental demographic shift in human history.”
First Great Human Population Explosion: 60,000-80,000 Years Ago
Contrary to what had been previously thought the first human population explosion occurred with hunter-gatherers 60,000-80,000 years ago, not with the first farmers around 10,000-12,000, a genetic study suggested. Popular Archaeology reported: “The prevailing theory is that, as humans transitioned to domesticating plants and animals around 10,000 years ago, they developed a more sedentary lifestyle, leading to settlements, the development of new agricultural techniques, and relatively rapid population expansion from 4-6 million people to 60-70 million by 4,000 B.C. [Source: Popular Archaeology, September 24, 2013 \=/]
“But hold on, say the authors of a recently completed genetic study. Carla Aimé and her colleagues at Laboratoire Eco-Anthropologie et Ethnobiologie, University of Paris, conducted a study using 20 different genomic regions and mitochondrial DNA of individuals from 66 African and Eurasian populations, and compared the genetic results with archaeological findings. They concluded that the first big expansion of human populations may be much older than the one associated with the emergence of farming and herding, and that it could date as far back as Paleolithic times, or 60,000-80,000 years ago. The humans who lived during this time period were hunter-gatherers. The authors hypothesize that the early population expansion could be associated with the emergence of new, more sophisticated hunting technologies, as evidenced in some archaeolocal findings. Moreover, they state, environmental changes could possibly have played a role. \=/
“The researchers also showed that populations who adopted the farming lifestyle during the Neolithic Period (10,200 – 3,000 B.C.) had experienced the most robust Paleolithic expansions prior to the transition to agriculture. “Human populations could have started to increase in Paleolithic times, and strong Paleolithic expansions in some populations may have ultimately favored their shift toward agriculture during the Neolithic,” said Aimé. The details of the study have been published in the scientific journal, Molecular Biology and Evolution, by Oxford University Press.” \=/
Why Did Modern Humans Survive and All Other Hominin Die Out
Why did our close relatives — namely Neanderthals, the recently discovered Denisovans and the hobbit people of Indonesia—die out while we went on to rule the world.Paleoanthropologist Rick Potts, director of the Smithsonian Institution’s Human Origins Program, argues that it is because unique adaptability of Homo sapiens. [Source: Jill Neimark. Discover, February 23, 2012]~||~
Potts told Discover magazine: “My view is that great variability in our ancestral environment was the big challenge of human evolution. The key was the ability to respond to those changes. We are probably the most adaptable mammal that has ever evolved on earth. Just look at all the places we can live and the way we seek out novel places to explore, such as space. The classic view of human evolution doesn’t emphasize adaptability. It focuses more on the idea that we were inevitable: that famous march from ape to human. It’s a ladder of progress with simple organisms at the bottom and humans at the top. This idea of inevitability runs deep in our societal assumptions, probably because it’s comforting—a picture of a single, forward trajectory, ending in modern humans as the crown of creation. ~||~
“The tremendous fossil discoveries of late have given us a lot more knowledge about the diversity of human experiments, and diversity is the theme that needs to be underlined. Yet in spite of the great variety in earlier human species, we are the only one that remains of a diverse family tree. That might seem to indicate something special about us, but in fact even we barely made it. Between 90,000 and 70,000 years ago, our own species almost bit the dust. Several genetic studies show a bottleneck back then, a time when the total number of Homo sapiens was tiny. So we, too, were an endangered species.~||~
“You can go back more than 3 million years to Australopithecus afarensis [the famous “Lucy” species], which over time maintained the ability to walk on two legs and to climb in trees. That’s a primal adaptable feature near the root of our evolutionary tree, and it allowed this species to make its way between areas of woodland and open savannas to find food. Stone tools, which first emerged 2.6 million years ago, are another feature of our adaptability. When it comes to acquiring and processing food, a hammerstone is better than a big molar, and a knapped flint is sharper than a pointed canine. All manner of foods opened up to the genus Homo with stone tools. ~||~
“The emergence of a large brain, with complex connectivity among neurons, suggests that the brain itself is an organ of adaptability. It allows us to take in information about the environment, organize, form social alliances, and raise the probability of survival in difficult times. You can see in the archaeological record that our early ancestors transported food from the place it was found to another place where members of the social group would meet. We modified the shapes of stones, we carried food, made fire and protective shelters, and we eventually began to cultivate crops and manipulate the environment in order to grow them. All of these small ways of altering the immediate surroundings strike me as reasonable adaptations to the instability of habitats.” ~||~
Modern Humans Adaptability to Climate Change in the Past
In the discussion of how human adaptability helped us dominate the world, paleoanthropologist Rick Potts, director of the Smithsonian Institution’s Human Origins Program, told Discover magazine: “I first got interested in this idea during my excavations in southern Kenya, where the changes in different layers of sediment, indicating different habitats at different times, were really obvious. Every layer suggested a change in vegetation as well as moisture, the kinds of other animals that were around, and the survival challenges faced by our ancient predecessors. I wondered if our lineage thrived precisely because our ancestors could adjust to those changes. I called this hypothesis variability selection—the idea that change itself was a selective pressure. Repeated, dramatic shifts in the environment challenged many species and may have actually selected for the features that have come to typify Homo sapiens, especially our ability to alter our immediate surroundings. [Source: Jill Neimark. Discover, February 23, 2012 ~||~]
“In the classic view, it was thought that we emerged on the savanna as conditions dried and cooled. We imagined our earliest ancestors in a backdrop of dry and grassy plains that basically forced the emergence of walking upright, tool use, and a larger brain, ultimately leading to language and culture and global success. ~||~
“Now, it’s certainly true that there has been marked global cooling and drying over the last 70 million years. But during the period of human evolution [since the appearance of our first direct ancestors in Africa], there were actually very pronounced fluctuations between warm and cool, between moist and arid. One way you can tell is by looking at different oxygen isotopes in the fossilized skeletons of ocean microorganisms. A heavier isotope is present during cooler periods, and a lighter one in warmer periods. I plotted out the variability in million-year intervals and found that about 6 million years ago, that variability went off the charts and kept increasing. That struck me as really strange, because that’s the time when the human story begins. African environments showed especially strong shifts between arid and moist climates during the past 4 million years. ~||~
“Our ancestors had to survive all these settings. I started to think, What if all that variability is not noise in the overall cooling and drying trend, but a very important test of the capacity of a creature to survive? This idea helps explain how we started out as a small, apelike, herbivorous species 6 million years ago in tropical Africa, and after a history of origin and extinction of species, what’s left today is us: a single species all over the planet with an astonishing array of abilities to adjust.” ~||~
Accelerated Evolution
The conventional wisdom for a long time was that humans had mastered their environments so well starting around 10,000 years ago, when agriculture was invented, it was no longer necessary to evolve. University of Michigan paleoanthropologist Milford Wolpoff told the Los Angeles Times, “People thought that with technology and culture there’d be no reason for physical things to make any difference. If you can ride a horse, it doesn’t matter if you can runs fast.”
But it turns nothing could be further from the truth: the speed of evolution for mankind is speeding up not slowing down, with some scientists estimating the pace is 100 times more than it was 10,000 years ago if no other reason than that there are many more people living in the world today. Wolpoff said, “When there’s more people, there are more mutations. And when there’s more mutations there’s more selection.”
In 2007, scientists compared 3 million genetic variants in the DNA of 269 people of African, Asian, European and North American descent and found 1,800 genes had been widely adopted in the last 40,000 years. Using more conservative methods, researchers came with 300 to 5000 variants, still a significant numbers. Among the changes that have occurred in the last 6,000 to 10,000 has been the introduction of blue eyes. That long ago nearly every one had brown eyes and blue eyes were non existent. Now there are half a billion people with them.
Image Sources: Wikimedia Commons, Nature, phys.org and Natural History magazine
Text Sources: Live Science, Nature, National Geographic, New York Times, Washington Post, Los Angeles Times, Smithsonian magazine, Nature, Scientific American. Discover magazine, Discovery News, Natural History magazine, Archaeology magazine, The New Yorker, Time, BBC, The Guardian, Reuters, AP, AFP and various books and other publications.
Last updated May 2024