The bones of modern people over the past millennia have become less dense, scientists have found. The lower jaw was reduced, which made it possible to pronounce more complex sounds. But relatively recently, the human skeleton was replenished with new bone. Now many have 208 instead of 207.
Millions of years ago, at the dawn of the formation of the human species, a small bone, a flabella, disappeared from the knee as unnecessary. Recently, they began to find her again.
Flabella is one of the sesamoid bones located in the tendons. In animals, it was formed about two hundred million years ago to give strength to joints, to protect the tendon from damage under heavy loads. In humans, this bone is believed to increase the mechanical resistance of the gastrocnemius muscle. But why is this necessary?
Scientists from Imperial College London (UK) analyzed 66 scientific papers dating back to 1875 containing information about flabella. It turned out that it occurs in 36, 8 percent of cases more often in Asians, inhabitants of Oceania and South America, and if we take into account gender, it is more preferable in men. In general, in 2018, this bone is common in the human population 3.5 times more often than a century ago - in 1918.
The growth of the flabella is genetically determined, but its ossification in all occurs at different ages and, possibly, depends on mechanical reasons. It is most often seen in people over 70 years old, but it can manifest itself as early as 12 years old.
Flabella usually occurs in both knees and causes complications after joint replacement surgery. In the implant, its presence is not taken into account, and this causes pain when walking. As a result, the "extra" bone has to be removed.
It has also been noticed that some neuropathic diseases are common in people with flabella, and the risk of osteoarthritis of the knee doubles. But what is the cause and what is the effect is still unclear.
Flabbela - a tiny bone in the knee - has become increasingly common in humans over the past 150 years.
The skeleton of modern humans is lighter in comparison with the skeleton of ancestral forms. This was found by scientists from the UK, USA, Germany and South Africa. On this account there is a special term - "gracilization". It involves a decrease in strength and bone mass in relation to body weight.
It has been known for a long time that modern people are more "graceful" than ancient hominids. Anthropologists considered this to be the result of a change in lifestyle, where physical activity has become much less due to the automation of labor. But exactly how much lighter did our bones feel?
Scientists analyzed the cancellous bone of the upper and lower extremities in several extinct hominids, starting with Australopithecus, chimpanzees and modern humans. They were able to show an increase in gracefulness from more ancient to later representatives of the genus, but not smooth: the bones of the Neanderthals and modern intelligent people were almost as dense as the bones of ancient homo.
But today's people are distinguished by a lower bone density even compared to their direct ancestors who lived during the last glaciation 20 thousand years ago. Moreover, the bones of the lower extremities underwent gracilization to a greater extent. This supports the hypothesis of the authors of the work that the cause of anatomical changes is a sedentary lifestyle. The price to pay for a slim figure is osteoporosis of the bones.
Comparison of the density of the cancellous tissue of the bones of the upper and lower extremities in different hominids. In modern people, the density drops sharply
The jaw fell off
It used to be thought that the diversity of human languages was not related to anatomy. However, an international team of scientists, including representatives of the Kazan Federal University, proved the opposite. In their opinion, the labiodental sounds "f" and "v" appeared in speech after the Neolithic revolution, about six thousand years ago, due to the fact that the lower jaw was reduced.
The emergence of human speech was preceded by a long evolution of the skeleton and body, a number of key improvements, such as a drooping larynx. All this made it possible to invent thousands of sounds, which resulted in thousands of existing languages. However, as suggested by the American linguist Charles Hockett, the sounds "f" and "v" were then absent. People who lived by hunting and gathering, constantly chewing raw plant food, could not pronounce them because of the too massive lower jaw and teeth-to-teeth bite.
Calculations have shown that labiodental sounds require 30 percent less muscular effort if the bite allows the upper lip to touch the lower teeth. Scientists built a model and found that six to eight thousand years ago, labiodental sounds met with a probability of three percent among primitive Indo-European languages, and among modern languages - with a probability of 76 percent.
The authors of the work believe that the "innovative" bite has begun to spread in societies that have switched to cooking.
On the left is the skull of a modern man, on the right is a Neanderthal man. In humans, the lower jaw is smaller and the bite allows the upper lip to touch the lower teeth.
In a 2010 article, anthropologist Christina Schaffler of the Institute of Biochemistry and Biology at the University of Potsdam, Germany, drew attention to the fact that the skeleton of modern children is becoming weaker. The researcher rejected the genetic causes, as well as the lack of nutrition. One explanation remains - low physical activity.
A few years later, Schaffler and colleagues repeated the study, comparing data on large groups of schoolchildren from Germany and Russia aged six to ten years from 2000 to 2010. Scientists analyzed height, body mass index and calculated the external strength of the skeleton, based on the ratio of the width of the humerus and height.
They noticed that the body mass index in German schoolchildren has continued to rise over the past two decades, and the strength of the skeleton has been declining. For Russian schoolchildren who move more, walk more often, go in for sports more, these parameters are somewhat better. However, in boys, bone strength tends to deteriorate.
Scientists hypothesize that the fragility of the skeleton and the shrinkage of the shoulder bones is an adaptation to a sedentary lifestyle and an increase in adipose tissue in the body.
Running from stress
Another interesting fact about the skeleton: it turns out that it plays an important role during times of stress. In the face of danger, the brain gives the command to react: run away or defend. At the same time, the body temperature rises, energy consumption increases, and the heartbeat increases. All this happens with the help of various hormones.
Scientists from the United States and India have shown that the hormone osteocalcin, produced by bone cells by osteoblasts, is also involved in this process. Experts conducted experiments on mice, causing them acute stress in response to a forced confinement and electric shock and measuring the level of this hormone. On average, in experimental animals under stress, the indicator increased by 50 and 150 percent, respectively. The authors ranked it as a fitness hormone and put forward the idea to develop anti-aging drugs based on it.
The brain makes the body react to danger with hormones. When a signal is received, the bones of the skeleton also release the active form of the hormone osteocalcin, which helps to cope with stress.