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Neanderthal bones: Signs of their sex lives
Inbreeding leads to a problematically small gene pool.
The site is infamous among anthropologists who study the Paleolithic period for the evidence of what appears to be the massacre and possible cannibalization of a family: Their bones seem to have been hacked at by stone tools and hammers, probably by another group of Neanderthals, to remove their flesh and marrow.
But more importantly, for this story, those bones also reveal something of the sex life of the cave's inhabitants. Anomalies and deformations, along with the DNA buried within their bones, suggest that the members of this group (and their parents) were mating with their close kin.
Lately, much news from the field of paleoarchaeology and anthropology has centered on Neanderthal bedfellows. You would be forgiven for thinking that paleoanthropologists think about little other than paleo-sex. Within the past several years, genetic evidence has emerged that Neanderthals interbred on more than one occasion with both anatomically modern humans and our newfound ancient relative, the Denisovans. One finger bone fragment from Denisova Cave in Siberia is now famous for belonging to a teenage girl who had a Neanderthal mother and a Denisovan father.
But evidence also shows that while some Neanderthals were apparently breeding well outside of the family group, some were also finding mates much closer to home.
In the remains from El Sidrón Cave, paleoanthropologist Luis Ríos and colleagues found 17 examples of congenital anomalies—structural malformations of various body parts that occur while an individual is developing in the womb.
One young El Sidrón individual, for example, had an oddly shaped patella, the bone that forms the kneecap: It had three lobes rather than just one. This Neanderthal probably had a limp. An adult male in the same cave had a markedly narrow nasal passage and a "retained deciduous mandibular canine," writes Ríos and his co-authors—this adult Neanderthal never lost one of his lower canine baby teeth. That tooth developed a painful cyst, which left its mark on the bone of his jaw. Microscopic striations on the tooth itself suggest that he coped with the pain by avoiding chewing on that side of his mouth.
One possible explanation for these skeletal abnormalities is that they resulted from extremely stressful environmental conditions, such as brutally cold weather and scarce food. A pregnant mother experiencing a lot of physical stress and nutritional deprivation might give birth to an infant with some of the same conditions seen at El Sidrón.
Inbreeding leads to a problematically small gene pool
But DNA tests from these bones indicate that inbreeding and a small population size were likely factors contributing to the physical peculiarities in this family. The 13 El Sidrón Neanderthals share much longer segments of their DNA than would be expected if they were the offspring of non-relatives.
Genetically, the three adult males in the group were closely related enough to be brothers, cousins, or uncles, while the four adult females in the group came from three distinct genetic lines. While all individuals were likely distantly related to one another (think third or fourth cousins), it is likely that the males exchanged females with another local, slightly less closely related group.
Today inbreeding carries connotations of "kissing cousins" or intimacy between even closer familial relations. But the term simply means mating between relatives, which increases the number of common ancestors in a family tree and the likelihood of inheriting deleterious genes from those common ancestors. Even third or fourth cousins are genetically similar enough for issues to arise.
The younger El Sidrón individuals (ranging in age from 5 to 15 years of age, along with one infant) were likely the offspring of at least some of the adults. At least one of these children, the young male mentioned above, possessed skeletal malformations that were likely passed down from parents who were fairly closely related.
The tangled familial ties of the El Sidrón Neanderthals are not a unique situation; DNA evidence from other Neanderthals elsewhere in Eurasia also shows elevated instances of shared DNA segments around this time, suggesting that mating between individuals who shared recent ancestors was fairly frequent, and possibly unavoidable, if local populations were small.
In general, inbreeding leads to a problematically small gene pool. Rare harmful traits that might disappear in larger populations tend to be amplified if close kin interbreed. Yet inbreeding has happened throughout human history, especially in the royal families of different cultures. Just look at the Habsburg family line in Spain or the royal families of Ancient Egypt to see the effects of keeping family bloodlines "pure."
Neanderthals were not the only ancient hominins to mate with their close relatives. Anatomically modern humans have also been found with skeletal evidence of inbreeding, such as abnormally bowed thigh bones, deformed arm bones, and even a case of a toddler with a swollen brain case consistent with hydrocephalus.
At the time that these congenital malformations appear, between 100,000 and 50,000 years ago, modern humans were traveling out of Africa. They fanned out across vast geographical regions, and, at times, were quite isolated from one another. Populations might have been separated by hundreds of kilometers at a time, only rarely encountering one another. This might be a simple reason why inbreeding occurred: Pickings were slim.
During the time that the El Sidrón Neanderthal family occupied their cave, it is likely that they were also fairly isolated. Their mating patterns probably had much more to do with small population size and low population density than any sort of cultural practice. There is no way to know if cultural taboos against mating with close relatives existed back then.
Interestingly, most of the individuals in the El Sidrón family group lived well past infancy despite physical conditions that, in some cases, would have made it difficult for them to get around and perform their day-to-day tasks. This family cared for one another, sharing physical burdens and helping each other to survive. Their relations, and their care, are recorded in their bones.
This column is part of an ongoing series about the Neanderthal body: a head-to-toe tour. See our interactive graphic.
- Ancient Neanderthal DNA Shows What They Ate—And Who They ... ›
- Sex with Neanderthals helped modern humans survive, says study ... ›
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How can we promote the creation of new neurons - and why is it so important?
- Neurogenesis, the birth of neurons from stem cells, happens mostly before we are born - as we are formed in the womb, we are generating most of what we need after birth.
- After birth, neurogenesis is still possible in two parts of the brain: the olfactory bulb (which is responsible for our sense of smell) and the hippocampus (which is responsible for memory, spatial navigation, and emotional processing).
- Research from the 1960s proves creating new neurons as adults is possible, and modern-day research explains how (and why) we should promote new neuron growth.
Two parts of the brain can continue growing through neurogenesis<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMjkyMzk2NS9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYwOTAwODc1MH0.4GDLlZmkwuD0-pJ0s0UWcUoYXMy95a-AM61a_QAlAeA/img.jpg?width=980" id="2e77e" class="rm-shortcode" data-rm-shortcode-id="4e23499fdf3b2185533979083fd02db7" data-rm-shortcode-name="rebelmouse-image" alt="brain made of twigs and plants concept of neurogenesis" />
Neurogenesis is still possible well into adulthood in two very important parts of the human brain.
Image by EtiAmmos on Shutterstock<p>Although most people are aware that aging or bad habits such as heavy alcohol use can contribute to the deterioration of our brains, not many of us give thought to how we can generate new brain cells.</p><p>Neurogenesis, the birth of neurons from stem cells, happens mostly before we are born - as we are formed in the womb, we are generating most of what we need after birth. </p><p><strong>After birth, however, neurogenesis is still possible in two parts of the brain:</strong></p><ul><li>The olfactory bulb, which is a structure of the forebrain that's responsible for our sense of smell. </li><li>The hippocampus, which is a structure of the brain located within the temporal lobe (just above your ears) - this area is important for learning, memory, regulation, of emotions and spatial navigation. </li></ul><p>Of course, when this information first came to light <a href="https://www.ncbi.nlm.nih.gov/pubmed/13860748" target="_blank">back in the 1960s</a>, the next natural question was: How do we promote neurogenesis in those areas where it's still possible? </p><p>Researchers today believe there are activities you can do (some of them may be things you already do on a daily basis) that can promote neurogenesis in your brain. </p><p><strong>Why is it important to promote the growth of new neurons in adulthood?</strong></p><p>We produce an estimated 700 million neurons per day in the hippocampus - this means by the time we reach the age of 50, we will have exchanged the neurons we were born within that area of the brain with new (adult-generated) neurons. </p><p>If we don't promote this exchange with the growth of new neurons, we may block certain abilities these new neurons help us with (such as keeping our memory sharp, for example). </p>
4 ways to promote neurogenesis in your brain<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yMjkyMzk2Ni9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYyNTE3NjczNH0.qyzh_AIUPKfaQIa1QEq4yTNCAAK9nYkH3HFV9vWXwww/img.jpg?width=1245&coordinates=0%2C0%2C0%2C104&height=700" id="64a68" class="rm-shortcode" data-rm-shortcode-id="ee1307fe2dd61ae425552da56db3c5ff" data-rm-shortcode-name="rebelmouse-image" alt="child playing trumpet concept of learning a new instrument neurogenesis" />
Learning a new instrument helps promote neurogenesis.
Photo by DenisProduction.com on Shutterstock<p><strong>Intermittent fasting</strong></p><p><a href="https://law.stanford.edu/2015/01/09/lawandbiosciences-2015-01-09-intermittent-fasting-try-this-at-home-for-brain-health/" target="_blank">A 2015 Stanford study</a> examined the link between <a href="https://www.healthline.com/nutrition/6-ways-to-do-intermittent-fasting#section1" target="_blank">intermittent fasting</a> and neurogenesis. Calorie restriction and fasting can not only increase synaptic plasticity and promote neuron growth but it can also decrease your risk of developing neurodegenerative diseases and boost cognitive function. </p><p><u>Two of the most common ways you can intermittently fast are: </u></p><ul><li>16 hours per day every day - this is a method where you are able to eat for an 8 hour period of the day and fast for 16 hours of the day. Many people begin their "fast" after dinner, pushing their morning meal far enough towards lunch that most of their "off" eating time happens while they are asleep anyways. </li></ul><ul><li>24 hours every week - this is a method where once a week you fast for an entire day. Some people prefer this method because the rest of the week can resume as normal - but for many, this is a difficult way to fast. </li></ul><p><strong>Traveling to new places</strong></p><p>While traveling is something many of us enjoy — scenic routes and new fun experiences — these things also promote neurogenesis while we're on vacation. <a href="https://www.chicagotribune.com/travel/ct-xpm-2014-01-28-sc-trav-0128-travel-mechanic-20140128-story.html" target="_blank">Paul Nussbaum</a>, a clinical neuropsychologist at the University of Pittsburgh, explains that the mental benefits of traveling are very clear.<br></p><p><em>"When you expose your brain to an environment that's novel and complex or new and difficult, the brain literally reacts. Those new and challenging situations cause the brain to sprout dendrites (dangling extensions) which grow the brain's capacity." </em></p><p><strong>Learning a new instrument</strong></p><p>The mental health benefits of music have long been studied, but did you know that learning a new instrument can promote new neuron growth? </p><p>According to <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2996135/" target="_blank">this 2010 study</a>, learning to play a new musical instrument is an intense, multisensory motor experience that requires that acquisition and maintenance of skills over your entire lifetime - which of course, promotes the new formation of new neural networks. </p><p>When is the best time to begin learning a new instrument? Childhood, of course. </p><p><em>"Learning to play a new musical instrument in childhood can result in long-lasting changes in brain organization," </em>according to the study mentioned above. </p><p>While learning an instrument in adulthood will also promote neurogenesis, children who began training with a musical instrument before the age of 7 have shown that they have a significantly larger corpus callosum (the area of the brain the allows communication between the two hemispheres of the brain) than many adults. </p><p><strong>Reading novels</strong></p><p>A study from <a href="http://esciencecommons.blogspot.com/2013/12/a-novel-look-at-how-stories-may-change.html" target="_blank">Emory University</a> showed there was an increase in ongoing connectivity in the brains of participants after reading the same (fiction) novel. </p><p>In this study, enhanced brain activity was observed in the region that control physical sensations and movement. Reading a novel, according to lead researcher Gregory Berns, can transport you into the body of the protagonist. </p><p>This ability to shift into another mental state is a vital skill that promotes healthy neurogenesis in those areas of the brain. </p>
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