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Why do some animals have beards?

Why do some animals have beards?


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Why do some animals such as some Goats, Ibex, Orangutan etc, have long well-shaped beard like men?


In humans and animals beard growth is usually restricted to males, since it's dependent on hormones (testosterone or, specifically, according to wikipedia it's dihydrotestosterone). By no surprise it starts growing during puberty.

But why?

Growing a long beard is costly concerning the necessary resources but also because of a potential handicap. Being able to afford a nice beard is showing dominance among males and attractiveness for females. It could be seen as a direct display of high testosterone levels. This is comparable to peacock feathers. They are very impractical, but have great value for showing dominance and attracting females.

I think, there are many psychological theories around to explain the attractiveness of beards. Some might also be meaningful in animals. Apart from cultural, religious or hipster beard trends, we generally consider old men with long beards as wise and knowledgeable. In animals the beard might also signal social status in groups, additionally to male dominance and sexual attraction.

Further reading:


Beards evolved to absorb a punch to jaw, study suggests

Facial hair may offer men more than just a stylistic choice, according to a new study, which suggests beards evolved to soften the impact of a punch and protect the jaw from harm.

Referencing Charles Darwin’s theory that a lion’s mane offers the animal protection, researchers recently conducted an experiment to decipher whether the same was true for humans.

According to the researchers, considering “the mandible, which is superficially covered by the beard, is one of the most commonly fractured facial bones in interpersonal violence,” it seemed likely beards are possible of providing “physical protection from strikes that would cause blunt trauma”.

To test the theory, the scientists created a fibre epoxy composite as a stand-in for the human jaw - as they noted that “it was not practical to obtain fully bearded skin samples from human cadavers” - which they then covered with sheepskin, before hitting with a blunt object.

For the experiment, the researchers used three types of sheep skin, with furred samples meant to mimic a full beard, sheared samples used to test whether the roots of hair follicles provided any protection and plucked samples meant to represent a hairless jaw.

Recommended

According to their findings, published in the journal Integrative Organismal Biology, facial hair is capable of lessening the impact of blunt trauma, such as that of a fist.

“The results of this study indicate that hair is indeed capable of significantly reducing the force of impact from a blunt strike and absorbing energy, thereby reducing the incidence of failure,” the researchers wrote. “If the same is true for human facial hair, then having a full beard may help protect vulnerable regions of the facial skeleton from damaging strikes, such as the jaw.

“Presumably, full beards also reduce injury, laceration, and contusion, to the skin and muscle of the face.”

Noting that they did not test it in the study, the scientists also speculated that it is “likely that the hair of beards helps deflect an oblique blow by reducing friction between the face and the object striking it” - meaning beards may provide a protective advantage in “male contest competition”. However, they did add that the results "provide no evidence that beards provide protection against being knocked out".

The researchers also suggested that the findings may “also explain why facial hair is associated with high masculinity, social dominance, and behavioural aggressiveness, as it may function as a true indicator of level of invulnerability to facial injury”.

While the study did find beards are capable of lessening the damage from a blow, the scientists acknowledged that human facial hair varies greatly across populations by coarseness, density and thickness, and that “future research should incorporate these measures to determine which types of facial hair may provide the best protection against impact”.


Contents

The beard develops during puberty. Beard growth is linked to stimulation of hair follicles in the area by dihydrotestosterone, which continues to affect beard growth after puberty. Dihydrotestosterone also promotes balding. Dihydrotestosterone is produced from testosterone, the levels of which vary with season. Beard growth rate is also genetic. [1]

Evolution Edit

Biologists characterize beards as a secondary sexual characteristic because they are unique to one sex, yet do not play a direct role in reproduction. Charles Darwin first suggested a possible evolutionary explanation of beards in his work The Descent of Man, which hypothesized that the process of sexual selection may have led to beards. [2] Modern biologists have reaffirmed the role of sexual selection in the evolution of beards, concluding that there is evidence that a majority of women find men with beards more attractive than men without beards. [3] [4] [5]

Evolutionary psychology explanations for the existence of beards include signalling sexual maturity and signalling dominance by the increasing perceived size of jaws clean-shaved faces are rated less dominant than bearded. [6] Some scholars assert that it is not yet established whether the sexual selection leading to beards is rooted in attractiveness (inter-sexual selection) or dominance (intra-sexual selection). [7] A beard can be explained as an indicator of a male's overall condition. [8] The rate of facial hairiness appears to influence male attractiveness. [9] [10] The presence of a beard makes the male vulnerable in hand-to-hand fights (it provides an easy way to grab and hold the opponent's head), which is costly, so biologists have speculated that there must be other evolutionary benefits that outweigh that drawback. [11] Excess testosterone evidenced by the beard may indicate mild immunosuppression, which may support spermatogenesis. [12] [13]

Ancient and classical world Edit

Lebanon Edit

The ancient Semitic civilization situated on the western, coastal part of the Fertile Crescent and centered on the coastline of modern Lebanon gave great attention to the hair and beard. Where the beard has mostly a strong resemblance to that affected by the Assyrians, and familiar to us from their sculptures. It is arranged in three, four, or five rows of small tight curls, and extends from ear to ear around the cheeks and chin. Sometimes, however, in lieu of the many rows, we find one row only, the beard falling in tresses, which are curled at the extremity. There is no indication of the Phoenicians having cultivated mustachios. [14]

Israel Edit

Israelite society placed a special importance on the beard. Many religious male figures are recorded to have had facial hair for example, numerous prophets mentioned in the Tanakh were known to grow beards. The Torah forbids certain shaving practices altogether, in particular Leviticus 19:27 states, "You shall not round off the side-growth on your head, or destroy the side-growth of your beard." [15] The Mishnah interprets this as a prohibition on using a razor on the beard. [16] This prohibition is further expanded upon in kabbalistic literature. [17] The prohibition carries to modern Judaism to this day, with rabbinic opinion forbidding the use of a razor to shave between the "five corners of the beard" – although there is no uniform consensus on where these five vertices are located.

According to biblical scholars, the shaving of hair, particularly of the corners of the beard, was originally a mourning custom [18] the behaviour appears, from the Book of Jeremiah, to also have been practiced by other Semitic tribes, [19] [20] [21] although some ancient manuscripts of the text read live in remote places rather than clip the corners of their hair. Biblical scholars think that the regulations against shaving hair may be an attack on the practice of offering hair to the dead, which was performed in the belief that it would obtain protection in sheol. [22] The prohibition may also have been an attempt to distinguish the appearance of Israelites from that of the surrounding nations, and likewise reduce the influence of foreign religions [23] The Hittites and Elamites were clean-shaven, and the Sumerians were also frequently without a beard [24] conversely, the Egyptians and Libyans shaved the beard into very stylised elongated goatees. [24] Maimonides criticises the shaving of the beard as being the custom of idolatrous priests. [25]

Mesopotamia Edit

Mesopotamian civilizations (Sumerian, Assyrians, Babylonians, Chaldeans and Medians) devoted great care to oiling and dressing their beards, using tongs and curling irons to create elaborate ringlets and tiered patterns.

Egypt Edit

The highest ranking Ancient Egyptians grew hair on their chins which was often dyed or hennaed (reddish brown) and sometimes plaited with interwoven gold thread. A metal false beard, or postiche, which was a sign of sovereignty, was worn by queens and kings. This was held in place by a ribbon tied over the head and attached to a gold chin strap, a fashion existing from about 3000 to 1580 BCE.

Indian subcontinent Edit

Ancient Indian warriors with various types of beards, circa 480 BCE.

Indian warrior Kunwar Singh of the Indian Rebellion of 1857 with a standard beard.

In ancient India, the beard was allowed to grow long, a symbol of dignity and of wisdom (cf. sadhu). The nations in the east generally treated their beards with great care and veneration, and the punishment for licentiousness and adultery was to have the beard of the offending parties publicly cut off. They had such a sacred regard for the preservation of their beards that a man might pledge it for the payment of a debt.

China Edit

Confucius held that the human body was a gift from one's parents to which no alterations should be made. [ citation needed ] Aside from abstaining from body modifications such as tattoos, Confucians were also discouraged from cutting their hair, fingernails or beards. [ citation needed ] To what extent people could actually comply with this ideal depended on their profession farmers or soldiers could probably not grow long beards as it would have interfered with their work. [ citation needed ]

Only a certain percentage of East Asian men are capable of growing a full beard. [ citation needed ] Another proportion of East Asian men are capable of growing facial hair but only in a very specific growth pattern in which hair only grows above the lip, below the lip and on the chin, with no hair growth on the cheeks or jaw. [ citation needed ] Another proportion of East Asian men are capable of growing facial hair in some combination of the two. [ citation needed ]

This growth pattern can be seen on the clay soldiers in the Terracotta Army.

Iran Edit

Close-up of one of the Lamassu beard relief in Gate of All Nations in Perspolis (south of Iran).

Fath-Ali Shah, the second Qajar Shah of Persia had a long beard.

The Iranians were fond of long beards, and almost all the Iranian kings had a beard. In Travels by Adam Olearius, a King of Iran commands his steward's head to be cut off, and on its being brought to him, remarks, "what a pity it was, that a man possessing such fine mustachios, should have been executed." Men in the Achaemenid era wore long beards, with warriors adorning theirs with jewelry. Men also commonly wore beards during the Safavid and Qajar eras.

Greece Edit

The ancient Greeks regarded the beard as a badge or sign of virility in the Homeric epics it had almost sanctified significance, so that a common form of entreaty was to touch the beard of the person addressed. [26] According to William Smith in these ancient times the moustache was shaven, leaving clear the space around the lips. [27] It was only shaven as a sign of mourning, though in this case it was instead often left untrimmed. [27] A smooth face was regarded as a sign of effeminacy. [28] The Spartans punished cowards by shaving off a portion of their beards. [29] Greek beards were also frequently curled with tongs. Anyway, youngsters usually did not wear a beard, moreover wearing a beard became optional for adults in the 5th and 4th century BCE. [30]

Macedon Edit

In Ancient Macedonia, during the time of Alexander the Great the custom of smooth shaving was introduced. [31] Alexander strongly promoted shaving during his reign because he believed it looked tidier. [32] Reportedly, Alexander ordered his soldiers to be clean-shaven, fearing that their beards would serve as handles for their enemies to grab and to hold the soldier as he was killed. [33] The practice of shaving spread from the Macedonians, whose kings are represented on coins, etc. with smooth faces, throughout the whole known world of the Macedonian Empire. Laws were passed against it, without effect, at Rhodes and Byzantium and even Aristotle conformed to the new custom, [34] unlike the other philosophers, who retained the beard as a badge of their profession. A man with a beard after the Macedonian period implied a philosopher, [35] and there are many allusions to this custom of the later philosophers in such proverbs as: "The beard does not make the sage." [36] Due to this association with philosophers, who lost reputation over time, the beard acquired more and more a negative connotation, as in Theodore Prodromos, [37] Lucian of Samosata [38] and Julian the apostate (who wrote the Misopogon, i. e. "beard hater").

Rome Edit

Shaving seems to have not been known to the Romans during their early history (under the kings of Rome and the early Republic). Pliny tells us that P. Ticinius was the first who brought a barber to Rome, which was in the 454th year from the founding of the city (that is, around 299 BCE). Scipio Africanus (236–183 BCE) was apparently the first among the Romans who shaved his beard. However, after that point, shaving seems to have caught on very quickly, and soon almost all Roman men were clean-shaven being clean-shaven became a sign of being Roman and not Greek. Only in the later times of the Republic did the Roman youth begin shaving their beards only partially, trimming it into an ornamental form prepubescent boys oiled their chins in hopes of forcing premature growth of a beard. [39]

Still, beards remained rare among the Romans throughout the Late Republic and the early Principate. In a general way, in Rome at this time, a long beard was considered a mark of slovenliness and squalor. The censors L. Veturius and P. Licinius compelled M. Livius, who had been banished, on his restoration to the city, to be shaved, to lay aside his dirty appearance, and then, but not until then, to come into the Senate. [40] The first occasion of shaving was regarded as the beginning of manhood, and the day on which this took place was celebrated as a festival. [41] Usually, this was done when the young Roman assumed the toga virilis. Augustus did it in his twenty-fourth year, Caligula in his twentieth. The hair cut off on such occasions was consecrated to a god. Thus Nero put his into a golden box set with pearls, and dedicated it to Jupiter Capitolinus. [42] The Romans, unlike the Greeks, let their beards grow in time of mourning so did Augustus for the death of Julius Caesar. [43] Other occasions of mourning on which the beard was allowed to grow were, appearance as a reus, condemnation, or some public calamity. On the other hand, men of the country areas around Rome in the time of Varro seem not to have shaved except when they came to market every eighth day, so that their usual appearance was most likely a short stubble. [44]

In the second century CE the Emperor Hadrian, according to Dio Cassius, was the first of all the Caesars to grow a full beard Plutarch says that he did it to hide scars on his face. This was a period in Rome of widespread imitation of Greek culture, and many other men grew beards in imitation of Hadrian and the Greek fashion. Until the time of Constantine the Great the emperors appear in busts and coins with beards but Constantine and his successors until the reign of Phocas, with the exception of Julian the Apostate, are represented as beardless. [27]

Celts and Germanic tribes Edit

Late Hellenistic sculptures of Celts [45] portray them with long hair and mustaches but beardless. Caesar reported the Britons wore no beard except upon the upper lip.

The Anglo-Saxons on arrival in Great Britain wore beards and continued to do so for a considerable time after. [46]

Among the Gaelic Celts of Scotland and Ireland, men typically let their facial hair grow into a full beard, and it was often seen as dishonourable for a Gaelic man to have no facial hair. [47] [48] [49]

Tacitus states that among the Catti, a Germanic tribe (perhaps the Chatten), a young man was not allowed to shave or cut his hair until he had slain an enemy. The Lombards derived their name from the great length of their beards (Longobards – Long Beards). When Otto the Great said anything serious, he swore by his beard, which covered his breast.

Middle Ages Edit

In Medieval Europe, a beard displayed a knight's virility and honour. The Castilian knight El Cid is described in The Lay of the Cid as "the one with the flowery beard". Holding somebody else's beard was a serious offence that had to be righted in a duel.

While most noblemen and knights were bearded, the Catholic clergy were generally required to be clean-shaven. This was understood as a symbol of their celibacy.

In pre-Islamic Arabia, Zoroastrians would apparently keep mustaches but shave the hair on their chins. The prophet Muhammad encouraged his followers to do the opposite, long chin hair but trimmed mustaches, to differ with the non-believers. This style of beard subsequently spread along with Islam during the Muslim expansion in the Middle Ages.

From the Renaissance to the present day Edit

Friedrich Engels exhibiting a full moustache and beard that was a common style among Europeans of the 19th century.


Behind the Beard: The Science of Facial Hair

Like a lot of young men today, and like my father before me, I have a beard. My beard is full and awesome, and it has really become a part of my identity over the last decade. A few years ago, I had an unfortunate shaving accident that left me without a proper beard for a couple of weeks, and my whole world changed - my dog treated me like a stranger, my friends and co-workers joked that I’d been replaced with a giant 12-year-old, and my wife threw away my razor to make sure I didn’t have any more shaving accidents in the future. My beard is an important part of who I am.

So, when I came across this article espousing some tangible benefits of facial hair on health and, my curiosity was piqued, and I did some more digging. I didn’t expect to find much, and so I was pleasantly surprised to discover a handful of peer-reviewed articles about beards and mustaches. Some of the findings were pretty intuitive, bordering on obvious. For instance, facial hair can help protect against harmful UV rays, and longer facial hair offers better protection than shorter hair (though neither do a very good job compared to real sunscreen). Another study reported that women judge men with beards to be older and have higher social status than men without beards, though beards didn’t affect attractiveness ratings.

One of the papers stood out from the crowd, in that it tried to explain why men might grow beards in the first place from an evolutionary perspective. Lots of other animals grow facial hair, and one of the most well-known cases is the lion’s mane. Only male lions grow manes, and males without manes are treated very differently than males with manes - they’re attacked more often, have less success with females, among other negative consequences. This suggests that there are survival and reproductive benefits to facial hair. The author proposes that beards might convey similar benefits to people, and specifically suggests that beards might act as a kind of camouflage to protect us from attacks to the fragile parts of our jaw. If you’re a boxer, this should make a lot of sense: one shot to the jaw can quickly incapacitate a person, so there’s a real benefit to making the jaw a little harder for an attacker to target. Of course, these kinds of theories are very tricky to test and disprove, so we may never know if there are survival benefits to facial hair, but it is an interesting idea.

Does this mean that all men should grow beards? Of course not. But if you do have a beard, and if your employer or significant other is giving you a hard time about it, now you can answer their complaints with, “Science says it’s good for me!” Please keep in mind, that none of this research applies to people with handlebar mustaches. I would argue that a handlebar mustache actually increases your chances of injury - in fact, if you have a handlebar mustache, please shave it immediately. I’m just looking out for your safety here.


Why Chimpanzees Have Big Testes, and Mandrills Have Small Ones

Katarina Zimmer
Apr 16, 2019

ABOVE: Chimpanzees lack fancy ornamentation, but have large testes in relation to their body size.
© ISTOCK.COM, IMPALASTOCK

B irds are well known for extravagant, sexually selected features such as peacocks’ tails, but primates too go out of their way to show off their good looks to potential mates. Some species display flashy ornaments designed to signal their dominance or attract females. Take the large cheek flanges of orangutans or the oversized noses of proboscis monkeys. But the ornaments don’t always match what’s under the hood, so to speak.

A comparative study of more than 100 primate species finds that males tend to have either large testes or flashy ornaments, but not both—suggesting an evolutionary trade-off between the two. The situation is different for canine teeth, which some species use as weapons: in fact, the larger the testes, the longer the canines tend to be, scientists reported April 10 in Proceedings of the Royal Society B.

“It’s great that this study has been done,” says Antje Engelhardt, a behavioral ecologist who studies primates at Liverpool John Moores University and wasn’t involved in the study. “We still know far too little about sexual ornaments, weapons, and also testes and sperm competition in primates.”

The authors—a group of Australian and Swiss researchers—turned to previous studies to gather data on sexually selected traits across a range of primate species, from bonobos to lemurs. These included figures on average testes size relative to body mass, as well as canine length and the expression of sexual ornaments in males relative to females. They also noted a number of social traits, such as the degree to which males monopolize access to females in a social group.

Using a statistical phylogenetic model, they uncovered several striking correlations in the data. Importantly, they found that larger testes tended to correlate with less pronounced sexual ornaments. “Bonobos or chimpanzees have huge testes relative to their body size, but they are otherwise quite modest-looking,” having no noticeable ornamentation at all, explains coauthor Stefan Lüpold, an evolutionary biologist at the University of Zürich.

Although some have taken this finding to mean that men with beards may have smaller testes, and the analysis did include humans, Lüpold stresses that this isn’t the case: the study compares variation across species and doesn’t draw any conclusions about variation within individual species, he warns. Besides, “you can shave the beard, and your testes don’t change.”

The researchers suppose the correlation has to do with the animals’ social mating systems: Chimpanzees and bonobos, which for the most part lack ornamentation, are by nature promiscuous species, females typically mating with multiple males. This means that within the female reproductive system, there’s competition among sperm to fertilize the egg. To secure better chances of outcompeting the gametes of rival males, it pays off to produce more sperm, and growing larger testes is one way to do that, Lüpold explains.

Paradoxically, the team found the opposite pattern when they examined the relationship between gonad size and weapons: Testes tended to be larger in species where males have longer canines relative to females, such as in long-tailed macaques. Both sexes tend to mate with multiple partners, and while the alpha male has the greatest access to females, he doesn’t entirely monopolize access to all of them. “Consequently, they have enlarged weapons—through priority access to females—but also relatively large testes because of some level of sperm competition,” Lüpold says.

Why ornaments trade off against testes size is unclear. The team suggests that canines and testes may not compete for the same developmental resources, whereas ornaments and testes would. In addition, fleshy ornaments or colorful skin could be more costly to grow and maintain than teeth, which once established don’t require much additional resources.

Engelhardt expressed surprise about the positive relationship between canines and testes size. Having both long canines and large testes might make sense for some primates, such as long-tailed macaque males, “but I would not expect that this is then something that comes out as a general trend,” she remarks.

Less surprising to Engelhardt is another correlation that Lüpold and his colleagues uncovered: that canine length and ornamentation go hand in hand. When they examined the relationship between canine length and the expression of ornaments alone, they found them to be positively correlated. Male mandrills and gelada baboons, for instance, both have relatively long canines as well as striking ornamentation compared to females, but also have smaller-than-average testes compared to other primates. This makes sense, says Engelhardt, because by using ornamentation to signal one’s strength, “the higher-ranking males would signal to the lower ranking ones that it wouldn’t make sense to challenge them, which would save both energy and potential injuries,” she says.

However, whether this interpretation holds water depends on the function of male ornaments, which isn’t well understood in primates. In some cases, ornaments could serve as signals of fighting ability or social status—so-called “badges of status”—but they could also signal attractiveness and viability to females, or both. The authors didn’t distinguish between these possibilities, Engelhardt cautions. “I would not necessarily mix those in one analysis, because the function is completely different,” she says.

Marion Petrie, an evolutionary biologist at Newcastle University, would like to see more within-species work exploring what information such ornaments convey to females. “Most of the literature on mating systems talks about the ability of males to monopolize females and the environmental factors that might lead to this. However, I am also interested in the female perspective,” she writes in an email to The Scientist. “Of course, one really needs to consider the costs and benefits to males and to females under both scenarios, but we seem to be a long way from understanding the drivers that result in one system predominating over the other.”

For her, the study illustrates the diversity of ways in which sexual selection operates across the animal kingdom. “We are only beginning to touch the surface of understanding it. There is so much we still don’t know about the evolution of the natural world and the sad thing is, we may never know as we are in real danger of losing it before we will ever find out.”

S. Lüpold et al., “Sexual ornaments but not weapons trade off against testes size in primates,” Proc R Soc B, doi:10.1098/rspb.2018.2542, 2019.


Cause of worst mass extinction ever found

Researchers figure out the function of mysterious heart structures first described by da Vinci.

The heart and the trabeculae.

Scientists found out the purpose of mysterious structures in the human heart, first described by Leonardo da Vinci 500 years ago. The mesh of muscle fibers called trabeculae lines the inner surface of the heart and was shown to affect how well the heart functions.

The mesh, exhibiting distinctive fractal patterns that resemble snowflakes, was initially sketched by Leonardo da Vinci in the 16th century. Early in human development, human hearts form trabeculaes, which create geometric patterns on the inner surface. While their purpose during this stage appears to be in aiding oxygenation of the growing heart, what they do in adults hasn't been previously figured out. Da Vinci thought the structure warms blood going through the heart.

To really understand what these networks do, an international research team used artificial intelligence to go through data from 25,000 MRI scans of the heart. They also looked at the related data pertaining to heart morphology and genetics.

The scientists observed that the rough surface of the heart ventricles helps the efficiency of the blood flow during a heartbeat, the way dimples on a golf ball lower air resistance, as elaborates the team's press release. They also discovered that there are six regions in human DNA that determine how exactly the fractal patterns in the muscle fibers form.

The team working on the project included Ewan Birney from the European Molecular Biology Laboratory's Bioinformatic Institute.

"Our findings answer very old questions in basic human biology," explained Birney. "As large-scale genetic analyses and artificial intelligence progress, we're rebooting our understanding of physiology to an unprecedented scale."

Another important insight – the shape of the trabeculae influences the heart's performance. Analysis of data from 50,000 patients established that the different fractal patterns can influence the risk of heart failure. Interestingly, the study showed that people who have more trabeculae branches seem to be at lower risk of heart failure.

Leonardo DaVinci: behind a Genius

Declan O'Regan, Clinical Scientist and Consultant Radiologist at the MRC London Institute of Medical Sciences, said that while their work is built on quite old observations, it can be crucial to today's people.

"Leonardo da Vinci sketched these intricate muscles inside the heart 500 years ago, and it's only now that we're beginning to understand how important they are to human health," said O'Regan. "This work offers an exciting new direction for research into heart failure, which affects the lives of nearly 1 million people in the UK."

Other participating scientists came from the Heidelberg University, Cold Spring Harbor Laboratory, and the Politecnico di Milano.

Check out their study published in the journal Nature.


Beards Probably Don’t Have Poop In Them (But They’re Still Dirty)

First, gross. But past reports that beards were laced with fecal matter were based on a single, solitary local news report, not rigorous scientific study. Although a spokesperson from Quest Diagnostics lab in Albuquerque did tell a reporter that a few bearded volunteers did have trace amounts of fecal matter in their beards (how? HOW?), these observations were not a part of any national trend. In other words, just because a couple of guys in New Mexico have poop in their beards doesn’t mean you do. But more recent research found that beards have more bacteria than dogs, so having a beard may warrant some extra time in the shower or an extra wipe.


Beards make men more attractive - but there's a catch

Men seeking a long-term relationship should dump the razor and invest in a beard comb, according to research into how attractiveness can be linked to hair length.

According to a study published in the Journal of Evolutionary Biology, women view men with stubble as more attractive for short-term flings than men with full beards, which were seen as more attractive for long-term relationships.

Investigators asked 8,520 women to rate photos of men for physical attractiveness in general, for a short-term or long-term relationship.

They manipulated the images to morph their facial hair from clean-shaven, through light and heavy stubble, to a full beard.

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'Incredibeards' in pictures

'Incredibeards' in pictures

Copyright: <a href="https://www.facebook.com/Incredibeard" target="_blank">Facebook/Incredibeard</a>

'Incredibeards' in pictures

'Incredibeards' in pictures

Copyright: <a href="https://www.facebook.com/Incredibeard" target="_blank">Facebook/Incredibeard</a>

'Incredibeards' in pictures

'Incredibeards' in pictures

Copyright: <a href="https://www.facebook.com/Incredibeard" target="_blank">Facebook/Incredibeard</a>

'Incredibeards' in pictures

'Incredibeards' in pictures

Copyright: <a href="https://www.facebook.com/Incredibeard" target="_blank">Facebook/Incredibeard</a>

The researchers also altered the men's brow ridge, cheekbones and jawline so they appeared more or less masculine.

Feminine faces were judged to be less attractive than unmanipulated faces when both were clean-shaven, while extremely masculine and extremely feminine-looking faces were judged the least attractive.

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Stubble was judged most attractive overall and received higher ratings for short-term flings, while full beards were seen as more attractive for long-term relationships.

The study's authors suggested beards may act as a signal of men's age and masculine social dominance. They also said strong masculine facial features, such as a pronounced brow ridge and robust jawline, may signal underlying health.

"Sexual selection via female choice has shaped the evolution of male ornamentation in many species," the study's authors wrote.


Science KS1/KS2: Why do animals and plants have camouflage?

Animals that are not well camouflaged are more likely to be eaten as prey.

Mutations are changes in genes that produce a beneficial or harmful trait.

After many generations the better camouflaged offspring will thrive and reproduce more.

Michaela models selection pressure by predators with a game involving sweets and salad.

This short film is from the BBC series, Evolutionwatch.

Teacher Notes

This short film could be shown before a school visit to an aquarium.

You could replicate the game with your class using sweets and salad, or with pieces of coloured wool on grass.

You could challenge your pupils to make camouflaged masks or camouflage themselves against different backgrounds.

Pupils could also design an animal that is camouflaged against a given habitat.

Curriculum Notes

This short film will be relevant for teaching primary science, particularly on the topics of animals and evolution.