Neanderthals: Facts About Our Extinct Human Relatives
A Neanderthal skull.
Credit: Jose Angel Astor Rocha | Shutterstock.com
Neanderthals (or Neandertals) are our closest extinct human relatives.
There is some debate as to whether they were a distinct species of the Homo genus (Homo neanderthalensis) or a subspecies of Homo sapiens.
Our well-known, but often misunderstood, fossil kin lived in Eurasia
200,000 to 30,000 years ago, in the Pleistocene Epoch. They started to
evolve 300,000 and 100,000 years ago, according to Encyclopedia Britannica.
Neanderthals' appearance was similar to ours, though they were shorter
and stockier with angled cheekbones, prominent brow ridges and wide
noses. Though sometimes thought of as dumb brutes, scientists have
discovered that they used tools, buried their dead and controlled fire,
among other intelligent behaviors. It is theorized that for a time,
Neanderthals probably shared the Earth with other Homo species.
Discovery
In 1856, a group of quarrymen discovered remnants of a skeleton in the
Neander Valley near Dusseldorf, Germany (hence their name). In a
limestone cave, they found 16 pieces of bone, including a skull.
Thinking the bones belonged to a bear, the quarrymen gave them to local
teacher Johan Karl Fuhlrott. From him, the bones found their way to
scientists, and it was eventually determined that they were ancient
human relatives. The publication and popularization of Charles Darwin's
"On the Origin of the Species" in 1859 helped inform the discovery.
Since that day in the Neander Valley, more than 400 Neanderthal bones
have been found.
The original cave men
Neanderthals lived during the Ice Age. They often took shelter from the
ice, snow and otherwise unpleasant weather in Eurasia's plentiful
limestone caves. Many of their fossils have been found in caves, leading
to the popular idea of them as "cave men."
Like other humans, Neanderthals originated in Africa but migrated to
Eurasia long before other humans did. Neanderthals lived across Eurasia,
as far north and west as the Britain, through part of the Middle East,
to Uzbekistan. Popular estimates put the peak Neanderthal population
around 70,000, though some scientists put the number drastically lower, at around 3,500 females.
While humans may have interbred with Neanderthals long ago, the pairing probably only rarely produced offspring.
Credit: Mauro Cutrona
Their short, stocky stature was an evolutionary adaptation for cold
weather, since it consolidated heat. According to the Smithsonian
Institution, the wide nose helped humidify and warm cold air, though
this assertion is debated.
The American Museum of Natural History states that other differences
from other humans are a flaring, funnel-shaped chest, a flaring pelvis,
and robust fingers and toes. Approximately 1 percent of Neanderthals had
red hair, light skin, and maybe even freckles.
Their brains, however, grew at slower rate than the brains of other
humans' and became larger, according to research published in the September 2017 issue of the journal Science.
"It took a little bit longer for the brain to grow in Neanderthals than
in modern humans," said study co-lead author Antonio Rosas, chairman of
the paleoanthropology group at Spain's National Museum of Natural
Sciences in Madrid. "We thought our slow way of growing was very
specific, very particular, very unique to our species," Rosas said.
"What we realize now is that this pattern of slow growth that allows us
to have this big brain and mature slowly, with all the advantages
involved with that, was also shared by different human species."
Social structure
Neanderthals lived in nuclear families. Discoveries of elderly or
deformed Neanderthal skeletons suggest that they took care of their sick
and those who could not care for themselves. Neanderthals typically
lived to be about 30 years old, though some lived longer. It is accepted
that Neanderthals buried their dead, though whether or not they left
carved bone shards as grave goods is debated.
It is not known if they had language, though the large size and complex nature of their brains make it a likely possibility.
Neanderthals used stone tools
similar to the ones used by other early humans, including blades and
scrapers made from stone flakes. As time went on, they created tools of
greater complexity, utilizing materials like bones and antlers. Evan
Hadingham of PBS's NOVA
reported that Neanderthals used a type of glue, and later pitch, to
attach stone tips to wooden shafts, creating formidable hunting spears.
Neanderthals had some control of fire, and it is even theorized that they built boats and sailed on the Mediterranean.
Neanderthals were primarily carnivorous, and the harsh climate caused them to resort occasionally to cannibalism. Recently, however, scientists have found that Neanderthals actually ate cooked vegetables fairly regularly.
Human-Neanderthal interbreeding
Probably the most debated aspect of Neanderthal life in recent years is
whether or not they interbred with other human species. The answer
remains ambiguous, with scholarly opinions ranging from belief that they
definitely interbred to belief that the two groups didn't exist on
Earth at the same time.
Neanderthal expert Erik Trinhaus
has long promoted the interbreeding hypothesis, but the theory really
caught fire when a 2010 study published in Science magazine determined
that Neanderthal DNA is 99.7 percent identical to modern human DNA (a
chimp's is 99.8 percent identical). Researchers
of the Neanderthal Genome Project found that 2.5 percent of an average
non-African human's genome is made up of Neanderthal DNA. The average
modern African has no Neanderthal DNA. This information could support
the interbreeding hypothesis because it suggests that Neanderthals and
other species only bred once the other humans had moved out of Africa,
into Eurasia, according to a 2012 paper published in the journal PLOS. They could have interbred as recently as 37,000 years ago.
Recent research published in the October 2017 issue of American Journal
of Human Genetics found that genomes of modern human groups originating
outside Africa contain between 1.8 and 2.6 percent Neanderthal DNA.
"Neandertal DNA is one source of variation for many traits in modern
humans," study lead author Michael Dannemann, a computational biologist
at the Max Planck Institute for Evolutionary Anthropology in Leipzig,
Germany, told Live Science. [Your Hair Color and Sleep Habits May Come from Neanderthals]
Another 2017 study by author Kay Prüfer, a paleogeneticist at the Max
Planck Institute for Evolutionary Anthropology in Leipzig, Germany,
found that modern-human DNA entered the Neanderthal gene pool between
130,000 and 145,000 years ago. [You May Be More 'Neanderthal' Than You Thought]
If this interbreeding occurred, why don't modern humans carry more
Neanderthal DNA? A possible reason involves the male sex chromosome.
Scientists have found that the Neanderthal Y chromosome may have kept
the two lineages from successfully interbreeding; the chromosome may
have created conditions that frequently led to miscarriages if or when a
Neanderthal male and modern human female got together, according to the
research published in the April 7, 2016, issue of the American Journal of Human Genetics.
In the study, Fernando Mendez, a population geneticist at Stanford
University, and colleagues discovered three mutations on the Y
chromosome of a Neanderthal male that would have produced molecules that
can trigger immune responses from women during pregnancy. Those immune
responses are linked to miscarriages.
A 2012 study,
however, cast doubt on the interbreeding theory. Researchers re-examined
bones from southern Spain that were used in earlier studies with new
radiocarbon dating techniques. They discovered that the Neanderthal
bones were more than 50,000 years old. Humans aren't believed to have
settled in the area until 42,000 years ago, meaning that it may be
unlikely that they lived together and interbred.
If humans and Neanderthals didn't interbreed, the similar genomes of
humans and Neanderthals could be the result of both groups having a
common African ancestor.
Extinction
No one knows exactly why Neanderthals went extinct and why Homo sapiens survived. Some scholars theorize that gradual or dramatic climate change
led them to their demise, while others blame dietary deficiencies. Some
theorize that humans killed the Neanderthals. Until recently the
hypothesis that Neanderthals didn't go extinct but simply interbred with
humans until they were absorbed into our species was popular.
Additional reporting by Alina Bradford, Live Science contributor.
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