Image: Evolution illustration
Duane Hoffmann / MSNBC illustration
Evolution didn't stop when the human species arose. So what will the descendants of present-day humans look like millions of years from now?
By
updated 4/30/2012 4:57:49 PM ET 2012-04-30T20:57:49

Natural forces of evolution still continue to shape humanity despite the power we have to profoundly alter the world around us, researchers say.

Evolution occurs in response to outside forces that weed out whatever individuals are least fit to survive those pressures, allowing those better-fit individuals to survive and reproduce. However, since humans radically alter their environments, some researchers have questioned whether natural forces of selection continue to act upon our species. For instance, agriculture can generate surplus food that can insulate us from many ills of the world.

The findings, detailed online Monday in the journal Proceedings of the National Academy of Sciences, add to accumulating evidence of our continued evolution. For instance, past research has suggested the human brain has been shrinking over the past 5,000 years. Another study of an island population in Quebec found a genetic push toward a younger age at first reproduction and larger families.

To explore this debate further, scientists examined church records of nearly 6,000 Finns born between 1760 and 1849, which detailed information on births, deaths, marriages and economic status. The data enabled the researchers to investigate human patterns of survival and reproduction and compare them with other species — genealogy is very popular in Finland, and the country has some of the best available data for such research.

"Studying evolution requires large sample sizes with individual-based data covering the entire life span of each born person," said researcher Virpi Lummaa at the University of Sheffield in England.

The researchers investigated how agriculture might have affected four key aspects of human life — survival to adulthood, access to mates, mating success and fertility per mate. Their findings suggest that farmer and fisher Finns continued to evolve just like other species. For instance, variations in fertility and survival to adulthood match patterns seen in other organisms. [ 10 Things That Make Humans Special ]

"We have shown advances have not challenged the fact that our species is still evolving, just like all the other species 'in the wild,'" Lummaa said.

Intriguingly, "both the relatively wealthy individuals were exposed to very similar overall selection as the poor in our study," said researcher Alexandre Courtiol, an evolutionary biologist at the Institute for Advanced Study in Berlin. "Many people intuitively think that 'wealth' might somehow protect us from the influence of the environment." Instead, both wealthy and poor seemed to experience similar levels of early survival and fertility.

As with most animal species, men and women are not equal when it comes to natural selection, the researchers found.

"Characteristics increasing the mating success of men are likely to evolve faster than those increasing the mating success of women," Courtiol said. "This is because mating with more partners was shown to increase reproductive success more in men than in women." In this case, men were more likely to remarry than women.

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The fact that natural selection continues to occur in humans during the advent of agriculture and other major cultural shifts "means that biology and culture must have interacted and shaped each other to an extent underestimated so far," Courtiol told LiveScience.

"Most scientists studying human evolution focus only on our hunter-gatherer way of life 10,000 years ago, but we show that, albeit interesting, this will not give you a complete picture of the story — we also need to focus on how people were living until very recently, and probably even today," Courtiol added.

"Extending our research toward modern days would be particularly interesting to understand how the current environment continues to shape humans," Courtiol said. "This could be potentially of importance from a medical point of view, to understand, for instance, how quickly our immunity can respond to new major epidemics. One major obstacle is that we need reliable data at the level of individuals — number of offspring, number of partners, birth and death date — across the lifetime of all born individuals, and such datasets are rare because even many famous longitudinal studies are biased towards certain types of people or do not cover all necessary life events."

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© 2012 LiveScience.com. All rights reserved.

Interactive: Before and after humans

Explainer: Ten fossils that tell the human tale

  • Frank Franklin II  /  AP file

    Where did we come from? Many truth seekers turn to faith and religion and find their answers therein. Others approach the question through a scientific lens and the theory of evolution. They have pieced together a tale of human origins from the fossils of our ancestors. The tale is incomplete and its telling reshaped with fresh interpretation of the growing fossil record.

    Click on the "Next" label to learn about ten fossil discoveries that have evolved the scientific rendering of human origins. In this image, a reconstructed Neanderthal skeleton is compared to a modern human.

    — John Roach, msnbc.com contributor

  • Toumai: Earliest-known ancestor of modern humans?

    MPFT

    Jaw fragments, isolated teeth and a skull excavated from the Sahel desert of Chad dated to between 6 million and 7 million years old may re-cast the opening chapter in the story of human origins. The fossils, revealed in 2001 and shown in this reconstruction, put the split in the evolutionary tree that eventually led to chimps on one branch and humans on the other more than 1,500 miles northwest of east Africa's Rift Valley, the current epicenter of research into human ancestors. But some scientists are not yet convinced the creature, named Sahelanthropus tchadensis and nicknamed Toumai, walked upright, which many scientists consider a key characteristic that distinguishes hominids from non-human primates.

  • Thigh bone suggests earliest two-legged walker

    Courtesy John Gurche, Brian Richmond via Science

    Analysis of a thigh bone amongst a clutch of fossils discovered in Kenya in 2000 and dated to nearly 6 million years ago may provide the earliest definitive evidence of a human ancestor that walked on two legs. Several detailed analyses of the femur, or thigh bone, shown here, have revealed it was adapted for upright walking. The bone belongs to a species known as Orrorin tugenensis. Most recently, U.S. scientists concluded the strategy first exhibited by this species for walking upright persisted for 4 million years, the majority of evolutionary history.

  • Middle Awash discovery fills gap in evolution story

    Tim D. White / Brill Atlanta

    Teeth and bones of the hand, foot, and thigh, shown here, are among the fossils of a 4.2 million-year-old Australopithecus anamensis specimen found in Ethiopia's Middle Awash region that has allowed scientists to link together their most complete chain of human evolution to date. The discovery helped fill a gap in the story, showing a likely transition between an earlier human ancestor known as Ardipithecus ramidus to the more recent australopithecines. The Middle Awash has yielded eight species in the story spanning 6 million years.

  • Lucy, the world's most famous fossil

    Dave Einsel  /  Getty Images

    Lucy, a 3.2 million-year-old Australopithecus afarensis named after the Beatles song "Lucy in the Sky with Diamonds," is perhaps the world's most famous fossil. She was discovered in the Afar region of Ethiopia in 1974 and remains among the most complete skeletons of an erect-walking human ancestor ever found, with about 40 percent of her bones intact. Her discovery allowed scientists for the first time to determine that upright walking predated the big brains of modern humans. Lucy's brain case is about the size of a chimp. In this photo, visitors view the Lucy skeleton at a Houston museum.

  • Taung child hailed as 'missing link' in 1924

    Denis Farrell  /  AP

    The diminutive fossil skull of 3.5-year-old early human ancestor, known as Taung child, was hailed as the "missing link" between apes and humans when it was discovered in 1924. Known scientifically as Australopithecus africanus, the discovery of the 2 million-year-old child also provided the first evidence that early humans evolved in Africa, rather than Europe, as many scientists believed at the time. In this photo, a researcher holds a replica of the skull as he makes the case that an eagle killed the Taung child.

  • Turkana boy, most complete skeleton found

    Sayyid Azim  /  AP

    Turkana boy, a nearly complete 1.6 million-year-old fossil of what some scientists call Homo ergaster, an early African population of Homo erectus, is considered the most complete skeleton of a prehistoric human ever found. The boy, who was discovered in 1984 in Kenya's Turkana region, stood 5-foot-3, indicating that hominids had gotten considerably taller and lankier since the days of Lucy, 3.2 million years ago. Plans to unveil Turkana boy at the National Museum of Kenya, shown here, in 2007 caused a stir between creationists and scientists.

  • Fossil discovery splinters human family tree

    Image: Casa Rinconada
    National Museums Of Kenya / F. Spoor  /  National Museum of Kenya via AP

    Many cartoons of evolution show a humpbacked ape slowly, linearly, progressing to a tall and erect modern human. Scientists long ago concluded that was too simple of a view, preferring instead to use a branching, thorny and knotted tree to depict the process. A discovery announced in 2007 threw yet another splinter in the picture. Many scientists had believed Homo habilis gave rise to Homo erectus who gave rise to modern humans. But the new finding shows habilis and erectus lived side by side for half a million years, raising doubt that habilis is a direct human ancestor. The scientists also found that erectus exhibited large size variation within the species, as shown in this image comparing two erectus skulls.

  • Neanderthals' relationship to modern humans fuzzy

    Image: Chankillo
    Image courtesy of National Academy of Sciences, PNAS

    The 1856 discovery of a skull cap and partial skeleton from a cave in Germany's Neander valley was the first recognized fossil human form. But exactly how the species, named in 1864 as Homo neanderthalensis, is related to modern humans remains the subject of fierce academic debate. Neanderthals occupied Europe and Asia from about 200,000 years to 30,000 years ago, overlapping in places with modern humans. Recent genetic analyses suggest little, if any, interbreeding between the species. Skeletal evidence, however, suggests Neanderthals were not very different than their modern human cousins. Even their brains were comparable to, if not bigger, than ours, as depicted in this Neanderthal reconstruction. Other studies have shown that like modern humans, Neanderthals used tools, wore jewelry, hunted, and buried their dead.

  • Hobbit discovery stuns the world, stirs debate

    Richard Lewis  /  AP

    As modern humans spread around the world over the past 160,000 years or so, a hobbit-like ancestor was holed up on the Indonesian island of Flores until at least 12,000 years ago, scientists announced at a press briefing in 2004, shown here. The stunning find has been scrutinized ever since. Some scientists agree the fossils represent a new species, Homo floresiensis. Others suggest the fossils belong to a diminutive race of modern humans, perhaps afflicted by one of several diseases associated with dwarfing.

  • Oldest modern humans found in Ethiopia

    Courtesy of Michael Day  /  AP

    The two partial skulls shown here of modern humans, Homo sapiens, were unearthed in Ethiopia in 1967. At the time, they were given a preliminary date of 130,000 years old. A 2005 revision using more modern dating techniques found them to be about 195,000 years old, making them the oldest known fossils of modern humans. Genetic evidence suggests modern humans arose in Africa about 200,000 years ago and then spread around the world, though other scientists hypothesize modern humans arose in parallel in Africa, Europe, and Asia.

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