Orangutans can communicate about the past just like humans, new research finds


Orangutans can communicate about the past just like humans, new research finds

The evolution of language converted a defenceless naked ape into a world-dominating force. It fundamentally transformed how humans transmit information and knowledge. A large and potent component of language is our ability to communicate about things that are not here, that happened in the past, or that will happen in the future. This feature of language is known as “displaced reference”.

Displaced reference is universal across the world’s languages and pervades our daily lives. In fact, to speak about the present moment has become a rarity nowadays, though noticeable exceptions are when we comment about the weather, ask for the salt over the dinner table, or talk with very young children.

Displaced reference unshackles speakers from the present. The magnitude of information that becomes available to individuals (or species) capable of displaced reference is therefore immeasurably greater than individuals (or species) strictly living in “the here and the now” – which is the bulk of the animal kingdom.

So far, besides humans, only social insects are capable of displaced reference. It is remarkable how honey bees (and their tiny brains) can communicate, for instance, about the location of distant food sources to other bees in the hive. The discovery of this fact merited a Nobel Prize in Physiology and Medicine for Karl von Frisch in 1973. Displaced reference in social insects spawns many fascinating – and unanswered – questions about animal intelligence and what the minimal viable intelligence systems for a particular cognitive capacity are.

However, biologically, bees and other insects are far apart from humans and can tell us very little about how language evolution played out among our ancestors. Lacking examples in vertebrates, mammals, or non-human primates, including great apes – our closest relatives – scientists literally had no clues about how this capacity came about in humans. But this is the new jigsaw piece that wild orangutans are bringing to the puzzle of language evolution.

The missing link?

In the low mountain rainforests of Sumatra, Indonesia, our team simulated a natural encounter with a predator to study the vocal responses of wild orangutan females. The set up consisted of a human researcher, disguised as a forest big cat, parading on all fours across the forest floor in front of the orangutan females.

The Sumatran tiger is one of the orangutan’s forest predators. Shutterstock

We observed that, despite showing all sorts of distress (including urinating and defecating), orangutan females refrained from responding vocally towards the “predator”. Instead, they waited up to 20 minutes to communicate their alarm to their offspring, long after the predator had left the scene. Across several experiments there was an average delay of seven minutes before the females vocally expressed their alarm.

The data (and simple common sense if we imagine ourselves facing a wild Sumatran tiger!) suggest that to respond vocally in the presence of a predator would have been a huge risk to the orangutans’ safety. If the females had responded immediately by calling out warnings, the predator could have detected them and perhaps attempted an attack, particularly on the infant orangutans.

Instead, the mothers waited for a significant amount of time before signalling vocal alarm about the danger that had now passed. The question that springs to mind, then, is: why did the females signal their alarm at all? If they hadn’t responded vocally at any point, they wouldn’t have faced any danger at all, right?

That is undoubtedly true; but had the mothers not expressed alarm, their infants would have remained oblivious to one of the most lethal dangers in the rainforest. Instead, the females waited long enough until it was safe to call out, but not so long that their infants could not connect their mothers’ vocal distress with what had just happened, and understand that it was extremely dangerous. The female orangutans were teaching their young about the dangers in the forest by referring to something that had happened in the (recent) past.

Orangutan offspring stay with their mothers as long as human children do. Shutterstock

In the 1970s, early attempts to release rescued orangutans and reintroduce them back into this same forest failed miserably. Nearly all the released animals fell prey to forest cats, essentially for lack of knowledge about survival in the rainforest.

Orangutan infants stay with their mothers as long as human children do. It has been shown that this exceptionally long period ensures that mothers pass on a variety of knowledge, skills and tools to their offspring. Our new findings indicate that teaching about predators is a vital aspect of this.

Widening this out to human language evolution, orangutans exemplify how our ancestors probably communicated beyond the here-and-now about the past, and possibly the future, even before they had uttered their first word. Together with mounting evidence, great apes are helping scientists build a clearer picture of our ancient ancestors as they moved towards fully fledged language.

By showing us that we are, after all, not so different from them, great apes help us learn where we come from, define who we are and, hopefully, decide where we are going as intelligent stewards of our precious planet.


To Rape is to Want Sex, Not Power

In the 1975 bestselling book: Against Our Will, the feminist writer, Susan Brownmiller, asserted that “rape is about power, not sex.” Ever since, the conventional wisdom has been that rapists are misogynistic men seeking domination and power over women, not violent men seeking sex.

However, there is a fundamental problem with Brownmiller’s bold assertion. In the ensuing 45 years, there has been no significant empirical research to support her claim. Yet, almost everyone repeats it.

In examining eight years of FBI data on 250,000 rapes and other sexual assaults, one factor stands head-and-shoulders above the others: the age range of the victims. Herein lies the key to unlocking the mystery of the offender’s motivation.

Social science has demonstrated a strong relationship between age and sexual attractiveness. Heterosexual men are sexually attracted to young women, while homosexual men are attracted to young men. The age preference explains why adult film stars, sex workers, exotic dancers as well as glamour models are often young, and why their earnings decline as they age.

Studying the ages of victims, therefore, provides an opportunity to examine sexual motivation. If rapists are primarily motivated by the desire for power and domination, then one would expect them to prefer middle-aged, career women. However, if rapists primarily desire sex, then one would expect them to prefer young women and men. Our research demonstrates that offenders almost always attack the young (see the figure below). The percentage of female victims who are over 50 is close to zero. Similarly, in male prisons, where women are extremely scarce, heterosexual men target the youngest inmates.

rapefigureMost recent discussions about sexual assault have focused on college students. However, it is high school kids that are at the greatest risk of being sexually assaulted. Our analyses of FBI data reveal that 15-year-olds are at the highest risk of sexual assault. They are about 9 times more likely to be raped than 35-year-olds.  Women rarely engage in sexual assault – they make up 3% of the offenders – but when they do commit sexual assaults, they most often target 15-year-olds. A power motive can’t explain why both male and female offenders prefer young victims. Only a sexual motive can do the job.

Sexual assault is as much a crime against young people as it is a crime against women. A 15-year-old male is more likely to be a victim of a sexual assault than a 40-year-old female. 15-year-olds may be at greater risk because their social life brings them into contact with potential rapists.  But difference in opportunity is only a partial explanation. An analysis of whether female robbery victims are sexually assaulted during the incident suggests that the sexual attractiveness of young people is an important factor. Since the robber has already established dominance over a vulnerable victim, the effects of opportunity and vulnerability are removed, and only the effect of the offender’s age preference remains. In such cases, robbers are much more likely to rape victims between the ages of 15 and 29the years when women (and men) tend to be the most sexually attractive. Only a sexual motive can account for this pattern.

Sexual offenders of all ages prefer young victims.  Even elderly offenders target 15-year-olds the most. Also, men who commit sexual assault tend to be considerably older than men who commit other types of violent crimes. The relatively high rate of sexual offending by older men is likely due to the fact that they have become less attractive with age while their sexual attraction to young people is undiminished. The men and women they find most attractive are not attracted to them.  Some of them use force to get their way.

Most date rapes occur during consensual sex when one partner, usually the man, wants to go further and the other does not. At the point of assault, men have an especially strong sexual drive. This is not to argue that men are overcome by desire. They can still control themselves, so sexual motivation is no excuse. However, arousal from any source increases impulsive behavior so it probably plays a role in date rape. The same goes for drugs and alcohol.

The reason most rapists target females is that a larger percentage of males are heterosexuals, not that they hate females. Homosexual men actually have as high an offense rate as heterosexual men. Gay men are just as likely to attack males as straight men are to attack females.

Any explanation of sexual assault must account for why gay men commit the crime at least as often as straight men. It must explain why offenders, regardless of age and gender, overwhelmingly target young people.   Most importantly, it must be based on solid social scientific evidence, not feminist orthodoxy. The evidence is substantial and it leads to a simple conclusion: most rapists force victims to have sex because they want sex.


Richard Felson is professor of sociology and criminology at Penn State University.

Richard Moran is professor of sociology at Mount Holyoke College, South Hadley MA.



  1. Richard B. Felson and Patrick Cundiff. 2014.  Sexual Assault as a Crime Against Young People.  Archives of Sexual Behavior.  43: 273-284.
  2. Richard B. Felson and Patrick Cundiff. 2012. Age and Sexual Assault During Robberies. Evolution and Human Behavior, 33: 10-16.
  3. Richard B. Felson, Patrick Cundiff, and Noah Painter-Davis. 2012. Age and Sexual Assault in Correctional Facilities: A Blocked Opportunity Approach. Criminology 50:887-912.

“The final result of sex development in humans is unambiguously male or female over 99.98% of the time”

“Evolution denialism is back, but this time it’s coming from left-wing activists who do hold power in academia.”


Evolutionary biology has always been controversial. Not controversial among biologists, but controversial among the general public. This is largely because Darwin’s theory directly contradicted the supernatural accounts of human origins rooted in religious tradition and replaced them with fully natural ones. The philosopher Daniel Dennett has described evolution as a sort of “universal acid” that “eats through just about every traditional concept, and leaves in its wake a revolutionized world-view, with most of the old landmarks still recognizable, but transformed in fundamental ways.” Fearing this corrosive idea, opposition in the US to evolution mainly came from Right-wing evangelical Christians who believed God created life in its present form, as described in Genesis.

In the 1990s and 2000s there were repeated attempts by evangelicals to ban evolution in public schools or teach the so-called “controversy” by including Intelligent Design—the belief that life is too complex to have evolved without the aid of some “Intelligent Designer” (i.e. God)—in the biology curriculum alongside evolution. But these attempts failed when scientists demonstrated in court that Intelligent Design was nothing more than Biblical Creationism gussied up in scientific-sounding prose. Since then, however, Creationism and Intelligent Design have lost a tremendous amount of momentum and influence. But while these right-wing anti-evolution movements withered to irrelevancy, a much more cryptic form of left-wing evolution denialism has been slowly growing.

At first, left-wing pushback to evolution appeared largely in response to the field of human evolutionary psychology. Since Darwin, scientists have successfully applied evolutionary principles to understand the behavior of animals, often with regard to sex differences. However, when scientists began applying their knowledge of the evolutionary underpinnings of animal behavior to humans, the advancing universal acid began to threaten beliefs held sacrosanct by the Left. The group that most fervently opposed, and still opposes, evolutionary explanations for behavioral sex differences in humans were/are social justice activists. Evolutionary explanations for human behavior challenge their a priori commitment to “Blank Slate” psychology—the belief that male and female brains in humans start out identical and that all behavior, sex-linked or otherwise, is entirely the result of differences in socialization.

This stance is maintained by the belief that evolutionary explanations for sex-linked behavioral differences are biologically essentialist, which is the fatalistic notion that biology alone directly determines our behavior. Blank Slate psychology, however, is universally rejected by experts, as the evidence for innate sex-linked personality differences in humans is overwhelmingly strong. But experts also universally reject that this view demands we embrace biological essentialism, because the environment does play a role, and observed sex differences are simply averages and overlap tremendously between the sexes. Sex no more determines one’s personality than it determines one’s height. Sex certainly influences these traits, but it does not determine them. For instance, most of us know females who are taller than most males, and males who are shorter than most females, though we are all aware that males are, on average, taller than females. In humans, the same is true for behavioral traits.

I am an evolutionary behavioral ecologist, and most of my work is concerned with how individual differences in behavior (i.e. personality) influence individual fitness, and the collective behavior and success of animal societies. Most are probably not aware, but animal personality research is a vibrant field within behavioral ecology due to the ubiquity of personality as a phenomenon in nature, and its ability to explain interactions both within and between species. In nearly every species tested to date for the presence of personality, we’ve found it, and sex-linked personality differences are frequently the most striking. Sex-linked personality differences are very well documented in our closest primate relatives, too, and the presence of sexual dimorphism (i.e. size differences between males and females) in primates, and mammals generally, dramatically intensifies these differences, especially in traits like aggression, female choosiness, territoriality, grooming behavior, and parental care.

Given that humans are sexually dimorphic and exhibit many of the typical sex-linked behavioral traits that any objective observer would predict, based on the mammalian trends, the claim that our behavioral differences have arisen purely via socialization is dubious at best. For that to be true, we would have to posit that the selective forces for these traits inexplicably and uniquely vanished in just our lineage, leading to the elimination of these traits without any vestiges of their past, only to have these traits fully recapitulated in the present due to socialization. Of course, the more evidenced and straightforward explanation is that we exhibit these classic sex-linked behavioral traits because we inherited them from our closest primate ancestors.

Counterintuitively, the social justice stance on human evolution closely resembles that of the Catholic Church. The Catholic view of evolution generally accepts biological evolution for all organisms, yet holds that the human soul (however defined) had been specially created and thus has no evolutionary precursor. Similarly, the social justice view has no problem with evolutionary explanations for shaping the bodies and minds of all organisms both between and within a species regarding sex, yet insists that humans are special in that evolution has played no role in shaping observed sex-linked behavioral differences. Why the biological forces that shape all of life should be uniquely suspended for humans is unclear. What is clear is that both the Catholic Church and well-intentioned social justice activists are guilty of gerrymandering evolutionary biology to make humans special, and keep the universal acid at bay.

Despite there being zero evidence in favor of Blank Slate psychology, and a mountain of evidence to the contrary, this belief has entrenched itself within the walls of many university humanities departments where it is often taught as fact. Now, armed with what they perceive to be an indisputable truth questioned only by sexist bigots, they respond with well-practiced outrage to alternative views. This has resulted in a chilling effect that causes scientists to self-censor, lest these activists accuse them of bigotry and petition their departments for their dismissal. I’ve been privately contacted by close, like-minded colleagues warning me that my public feuds with social justice activists on social media could be occupational suicide, and that I should disengage and delete my comments immediately. My experience is anything but unique, and the problem is intensifying. Having successfully cultivated power over administrations and silenced faculty by inflicting reputational terrorism on their critics and weaponizing their own fragility and outrage, social justice activists now justifiably think there is no belief or claim too dubious that administrations won’t cater to it. Recently, this fear has been realized as social justice activists attempt to jump the epistemological shark by claiming that the very notion of biological sex, too, is a social construct.

As a biologist, it is hard to understand how anyone could believe something so outlandish. It’s a belief on a par with the belief in a flat Earth. I first saw this claim being made this year by anthropology graduate students on Facebook. At first I thought they mistyped and were simply referring to gender. But as I began to pay closer attention, it was clear that they were indeed talking about biological sex. Over the next several months it became apparent that this view was not isolated to this small friend circle, as it began cropping up all over the Internet. In support of this view, recent editorials from Scientific American—an ostensibly trustworthy, scientific, and apolitical online magazine—are often referenced. The titles read, “Sex Redefined: The Idea of 2 Sexes Is Overly Simplistic,” and “Visualizing Sex as a Spectrum.”

Even more recently, the most prestigious scientific journal in the world, Nature, published an editorial claiming that classifying people’s sex “on the basis of anatomy or genetics should be abandoned” and “has no basis in science” and that “the research and medical community now sees sex as more complex than male and female.” In the Nature article, the motive is stated clearly enough: acknowledging the reality of biological sex will “undermine efforts to reduce discrimination against transgender people and those who do not fall into the binary categories of male or female.” But while there is evidence for the fluidity of sex in many organisms, this is simply not the case in humans. We can acknowledge the existence of very rare cases in humans where sex is ambiguous, but this does not negate the reality that sex in humans is functionally binary. These editorials are nothing more than a form of politically motivated, scientific sophistry.

The formula for each of these articles is straightforward. First, they list a multitude of intersex conditions. Second, they detail the genes, hormones, and complex developmental processes leading to these conditions. And, third and finally, they throw their hands up and insist this complexity means scientists have no clue what sex really is. This is all highly misleading and deceiving (self-deceiving?), since the developmental processes involved in creating any organ are enormously complex, yet almost always produce fully functional end products. Making a hand is complicated too, but the vast majority of us end up with the functional, five-fingered variety.

What these articles leave out is the fact that the final result of sex development in humans are unambiguously male or female over 99.98 percent of the time. Thus, the claim that “2 sexes is overly simplistic” is misleading, because intersex conditions correspond to less than 0.02 percent of all births, and intersex people are not a third sex. Intersex is simply a catch-all category for sex ambiguity and/or a mismatch between sex genotype and phenotype, regardless of its etiology. Furthermore, the claim that “sex is a spectrum” is also misleading, as a spectrum implies a continuous distribution, and maybe even an amodal one (one in which no specific outcome is more likely than others). Biological sex in humans, however, is clear-cut over 99.98 percent of the time. Lastly, the claim that classifying people’s sex based on anatomy and genetics “has no basis in science” has itself no basis in reality, as any method exhibiting a predictive accuracy of over 99.98 percent would place it among the most precise methods in all the life sciences. We revise medical care practices and change world economic plans on far lower confidence than that.

Despite the unquestionable reality of biological sex in humans, social justice and trans activists continue to push this belief, and respond with outrage when challenged. Pointing out any of the above facts is now considered synonymous with transphobia. The massive social media website Twitter—the central hub for cultural discourse and debate—is now actively banning users for stating true facts about basic human biology. And biologists like myself often sit quietly, afraid to defend our own field out of fear that our decade of education followed by continued research, job searches, and the quest for tenure might be made obsolete overnight if the mob decides to target one of us for speaking up. Because of this, our objections take place almost entirely between one another in private whisper networks, despite the fact that a majority of biologists are extremely troubled by these attacks to our field by social justice activists. This is an untenable situation.

It is undoubtedly true that trans people lead very difficult lives, which are only made more difficult by the bigotry of others. But social justice activists appear completely unwilling or unable to distinguish between people who criticize their ideology and people who criticize their humanity. Their social immune system appears so sensitive that it consumes itself. We need to acknowledge that trans issues and ideology are complex, and concern one of the most marginalized communities in the world. Because of this, we must give these issues the respect they deserve by approaching them with nuance and compassion instead of crudeness and cruelty. But we must not jettison truth in this process. If social justice activists require scientists to reject evolution and the reality of biological sex to be considered good allies, then we can never be good allies.

Back when evolution was under attack from proponents of Biblical Creation and Intelligent Design, academic scientists were under no pressure to hold back criticism. This is because these anti-evolution movements were almost exclusively a product of right-wing evangelicals who held no power in academia. Now we have a much bigger problem, because evolution denialism is back, but this time it’s coming from left-wing activists who do hold power in academia. This makes the issue both harder to ignore and harder to remove. Social justice and hyper-militant trans activism now seems to act as a kind of anti-universal acid, and not merely a strong buffer solution. While the universal acid of evolution eats through old cherished beliefs and replaces them with deeper understanding and a clearer picture of reality, the anti-universal acid of social justice ideology is a recklessly destructive force, aiming to abolish scientific truth and replace it with relativistic postmodern nonsense.

I did not train to be a scientist for over a decade just to sit quietly while science in general, and my field in particular, comes under attack from activists who subvert truth to ideology and narrative. When I reflect on my initial reasons over a decade ago for choosing a career as an academic scientist, it was largely due to the inspiration I felt from outspoken public intellectuals like Richard Dawkins, Sam Harris, Stephen Fry, and the late Christopher Hitchens, who led by example and followed reason wherever it took them. At the time, it seemed to me that a career as an academic scientist would be the most intellectually satisfying profession imaginable. It would allow me to dive deep into questions at the frontier of human knowledge, teach and train students to think critically, and pass on the virtues of boldly engaging with unreason in the search for truth to a new generation.

But it seems clear to me that academia now is not as it was advertised a decade ago when I started down this path. It is no longer a refuge for outspoken, free-thinking intellectuals. Instead, it seems one must now choose between living a zipper-lipped life as an academic scientist, or living a life as a fulfilled intellectual. Currently, one cannot do both.

Orangutans can communicate about the past just like humans, new research finds


Orangutans can communicate about the past just like humans, new research finds

The evolution of language converted a defenceless naked ape into a world-dominating force. It fundamentally transformed how humans transmit information and knowledge. A large and potent component of language is our ability to communicate about things that are not here, that happened in the past, or that will happen in the future. This feature of language is known as “displaced reference”.

Displaced reference is universal across the world’s languages and pervades our daily lives. In fact, to speak about the present moment has become a rarity nowadays, though noticeable exceptions are when we comment about the weather, ask for the salt over the dinner table, or talk with very young children.

Displaced reference unshackles speakers from the present. The magnitude of information that becomes available to individuals (or species) capable of displaced reference is therefore immeasurably greater than individuals (or species) strictly living in “the here and the now” – which is the bulk of the animal kingdom.

In 200 years, humans reversed a climate trend lasting 50 million years, study says


(CNN)What do scientists see when comparing our future climate with the past? In less than 200 years, humans have reversed a multimillion-year cooling trend, new research suggests.

If global warming continues unchecked, Earth in 2030 could resemble its former self from 3 million years ago, according to a study published Monday in the journal Proceedings of the National Academy of Sciences finds.
During that ancient time, known as the mid-Pliocene epoch, temperatures were higher by about 2 to 4 degrees Celsius (3.6 to 7.2 degrees Fahrenheit) and sea levels were higher by roughly 20 meters (almost 66 feet) than today, explained Kevin D. Burke, lead author of the study and a researcher and Ph.D. candidate at the Nelson Institute for Environmental Studies at the University of Wisconsin-Madison.
Today is “one of the most difficult scenarios we’ve ever found ourselves in,” Burke said. “This is a very rapid period of climatic change. Looking for anything that we can do to curb those emissions is important.”
Climate scientists say that our globe is about 1 degree Celsius hotter today than it was between 1850 and 1900 and that this is due in part to gas emissions from cars, planes and other human activities. Some gases, including carbon dioxide and methane, trap heat in the atmosphere, producing a “greenhouse effect” that makes the planet warmer.

Trying to make climate change vivid

The new study is basically “a similarity assessment,” Burke said. “We have projections of future climate available for the year 2020, 2030 and so forth.” For nearly 30 future decades, then, he and his co-authors drew future-to-past comparisons based on six reference periods.
The reference periods were the Historical, about mid-20th century; the Pre-Industrial, around 1850; the mid-Holocene, about 6,000 years ago; the last Interglacial Period, about 125,000 years ago; the mid-Pliocene, about 3 million years ago; and the early Eocene, about 50 million years ago.
If we continue our current level of greenhouse gas emissions — what some would say is a “business as usual” scenario — the overall global climate in 2030 will most closely resemble the overall climate of the mid-Pliocene period, Burke said.
What did Earth look like then? Annual temperatures on average were about 2 to 4 degrees Celsius warmer than today, there was little permanent ice cover in the Northern Hemisphere, and the sea level was about 20 meters higher.
In some places, though, including cities in the United States, temperatures in 2030 would be roughly double the global average.
Burke presented a second scenario: If we continue as we are doing now, “we see that by the year 2150, future climates have an analog [or equivalent] coming from the Eocene, the climate of 50 million years before present.”
“Proxies and models tell us that it may have been as much as, globally, on average 13 degrees Celsius [about 23 degrees Fahrenheit] warmer than present,” Burke said. “During that time period, there was essentially no permanent ice cover in either of the poles, so sea level would have been much higher as well.”
Although the geography and configuration of our continents and oceans were different at that time, there may have been swampy forests “as far north as locations in the Arctic Circle,” he said.
“Those different possible future outcomes are entirely dependent on the emissions scenario that we follow,” he said.
Burke admitted that “the climate in and of itself wouldn’t just wipe us out or anything,” but “it’s important to recognize that it would be a substantially different future.”

Disrupting the future of humanity

Flavio Lehner, a project scientist at the US National Center for Atmospheric Research, said what’s new in the study is the attempt to “draw parallels between past and future climates.”
Lehner, who was not involved in the research, said that comparisons to the past typically are complicated by “many uncertainties” that make it challenging to “reconstruct and understand hydroclimate change, even over the last 1,000 years.”
“The study here does not magically reduce these uncertainties but seems to circumvent the problem by relying heavily on climate model simulations of past climates,” he said. “That’s not necessarily a scientific breakthrough but still makes for an interesting study.”
Nick Obradovich, a research scientist in the scalable cooperation group at the MIT Media Lab, said “it is well-established that the rate of warming we are currently experiencing is remarkable relative to historical rates of warming.”
“Jumping back to climates not seen for millions of years — in the course of decades — will likely totally disrupt the future of humanity,” said Obradovich, who also was not involved in the research. “It’s very possible that both ecological systems and human systems may fail to adapt rapidly enough, with devastating consequences. No one knows exactly how this future will look, but if we don’t curtail emissions drastically and immediately, it isn’t likely to be a pretty one.”
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Burke emphasized, “This isn’t really a problem for the future; this is a problem for now. What we’re showing is that in the next decade or two, we may see climates like that of the Pliocene.”
To avoid that future, both political representatives and individuals need to take action to reduce greenhouse gas emissions, he said. Individually, we can take public transport or use bicycles instead of driving, he suggested. And we can eat less of a meat-based or beef-based diet.
“When you think about the number of people who could make a change like that, that could have a significant effect,” Burke said. “Anything that we can do to curb those emissions is important.”

Why Blood is Thicker than Water


People tend to favour relatives over non-relatives. But is this a product of culture or a part of human nature? 

Parts of this article were excerpted, with changes, from the book The Ape That Understood the Universe: How the Mind and Culture Evolve (2018. Cambridge University Press).

In 2011, the Australian state of Queensland suffered extreme flooding. As with any disaster, this one left many tales of heroism in its wake. Among the most poignant is the story of thirteen-year-old Jordan Rice. Jordan had been out shopping with his mum, Donna, and his younger brother, Blake. They were in the car heading home when, out of the blue, they found themselves caught in the middle of a flash flood. Unable to drive any further, and unable to get to dry land, the three scrambled onto the roof of the car and then sat there, stranded in the middle of a violent torrent of water.

Fortunately, some bystanders saw what had happened. One man – Warren McErlean – tied one end of a rope to a post, and the other around his waist, and then pushed his way through the rapidly rising waters to the car. He reached for Jordan, but Jordan pulled away, begging him to save his little brother first. McErlean complied: He picked Blake up and carried him quickly to safety. Before he had time to rescue the others, however, a sudden surge of water flipped the car. Jordan and his mum were swept away and killed.

By putting his brother ahead of himself, Jordan lost his life. From an ethical point of view, this represents the height of moral action. From a Darwinian point of view, on the other hand, it’s initially quite perplexing. Evolutionary theory seems to imply that the only organisms that prevail in the harsh Darwinian struggle for existence are those that look out for number one, and thus that the whole world will be populated with self-interested, self-serving organisms. But Jordan was no such organism; he risked his own life to save someone else, and died in the process. And although his was an extreme and extraordinary case, Jordan was no freak of nature – no moral equivalent of a two-headed gorilla. Self-sacrifice of one sort or another is nearly as common as breathing.

Evolutionary biologists call this the problem of altruism, and it’s occupied many of the greatest thinkers of the field. At one time, the problem looked intractable; today, however, we’ve got a powerful arsenal of theories aimed at explaining the evolution of altruistic behaviour. Arguably the most important – and certainly the one most applicable to the case of Jordan Rice – was the brainchild of the British biologist William D. Hamilton. Hamilton’s breakthrough is now known as kin selection theory, and it offers an explanation for one important type of altruism: altruism toward one’s relatives.

The details of Hamilton’s theory are complex, but the basic idea is fairly simple. The starting point is the observation that organisms share a larger fraction of their genes with relatives than they do with unrelated individuals. This has an important implication, namely that any gene that contributes to the development of a tendency to help one’s relatives has a better than average chance of being located as well in the recipients of that help. As a result, by helping one’s relatives to survive and reproduce, one can indirectly help to spread the genes that gave rise to that very tendency.

To be clear, people aren’t thinking about their genes when they help their relatives; they just help because they want to help. But why do they want to help? Why did evolution bequeath us this inclination? That’s the question that kin selection theory aims to answer.

Needless to say, humans can’t peer into one another’s genomes and directly perceive who their kin are. Strictly speaking, then, people couldn’t have evolved to favour kin. What could have happened, though, is that we evolved to follow certain implicit rules that, in our ancestral past, led us to favour kin over non-kin nine times out of ten. Several such rules have been proposed, among them: “Help people you were raised with or those you helped to raise,” and “Help people who resemble you more closely than the average person in your social environment.” Dispositions such as these could generate kin altruism even in the absence of any conception of kinship or desire to pass on one’s genes.

Consistent with Hamilton’s theory, various lines of evidence suggest that people do indeed favour their relatives over non-relatives in a wide variety of ways. Parents tend to be closer to biological children than stepchildren; will-makers tend to leave more money to relatives than non-relatives; and people of all stripes are more likely to risk life-and-limb to save relatives than anyone else (Jordan Rice is a case in point).

Why, though, should we favour the kin-selection explanation for these tendencies over a rather obvious competitor: the idea that we simply learn to favour our kin? I’ll give you three reasons.

First, the importance of kinship appears to be a human universal. Wherever in the world we look, people’s affinity for kin stands out like a sore thumb – or, more to the point, like an opposable thumb: a species-typical attribute with a clear adaptive rationale. In a wide-ranging survey of the anthropological literature, Essock-Vitale and McGuire found that, across cultures, people are more likely to help kin than non-kin in situations where there’s no expectation of payback. Similarly, Oliver Curry and colleagues surveyed the ethnographies of sixty historically independent cultures, tallying every passage that indicated either a positive or a negative view of kin altruism. The result? Kin altruism was seen as a moral good in 100% of cases.

Admittedly, the fact that a trait is universal doesn’t necessarily mean it has an evolutionary origin; if it did, we’d have to conclude that drinking Coca Cola and using mobile phones are products of natural selection. Still, cross-cultural universality sits a lot more easily with an evolutionary explanation than it does with a Nurture Only one. We’ve got a good understanding of how Coke and mobile phones came to be universal despite not being innate. Until advocates of the Nurture Only view can offer an equally good explanation for the universality of our kinship bias, the default prediction from the Nurture Only perspective is that, across cultures, people’s behaviour toward kin and non-kin will vary randomly with respect to kin selection theory: In some cultures, people will favour kin, in others they’ll favour non-kin, and in others still they’ll show no bias in either direction. That’s not what we see, though; people everywhere favour kin. This represents a major predictive failure for the Nurture Only view.

A second argument for an evolutionary explanation is that not only is our affinity for kin a cross-cultural universal, but it persists even when we try to eliminate it. An example comes from the Israeli communes known as kibbutzim. The kibbutzim were founded on radical socialist principles, and the founders sought to eliminate supposedly “bourgeois” traditions such as parents caring exclusively for their own biological children. To that end, kibbutz children were housed together in large communal quarters, rather than shacking up with their parents. But although this looked fine on paper, in practice it rapidly disintegrated. Parents hated it, and before too long started insisting that their children live with them. Some of the kibbutz men resisted for a while, but eventually they had to give in. Thus, rather than being a product of social pressure, the tendency to favour one’s kin survived even in spite of significant social pressure against it.

And this isn’t an isolated case. Another example comes from a polygynous Mormon community studied by William Jankowiak and Monique Diderich. Men in this community often had several wives, and thus siblings and half-siblings commonly ended up living together in the same home. Despite living together, however, and despite a community ethos which downplayed differences in relatedness among siblings, people were still closer to their full-siblings than their half-siblings. The relatedness bias runs deep – deeper than non-evolutionary theories can readily explain.

A third and final nail in the Nurture Only coffin is the fact that kin altruism is not unique to human beings. On the contrary, among group-living species, it’s virtually universal. Parent birds in some species fake injuries to lure hungry predators away from their nests and their baby chicks. Belding’s ground squirrels issue alarm calls to warn family members of encroaching predators. And worker bees sting any individual that ventures too close to the family hive, which protects the hive but also usually kills the worker. More generally, kin altruism is found throughout the length and the breadth of the animal kingdom.

And that’s just scratching the surface! Kin altruism is even found in plants. When American sea rocket shares soil with sibling plants, for instance, it grows its roots less aggressively and less competitively than it does when it shares soil with non-relatives. More remarkable still, kin altruism can even be found in bacteria: Bacteria cooperate more with closely related bacteria than with more remotely related bacteria. This means that a lot of kin altruism – indeed, the vast majority of the kin altruism taking place on the planet – is invisible to us. But it’s there, and it shows us that kin selection is profoundly important, not only in complex multicellular organisms such as ourselves and plants, but right across the living world.

The fact that kin altruism is so ubiquitous – vastly more so than Coke or mobile phones – tells us something important. It tells us that William Hamilton, in positing his kin selection theory, identified an extremely deep principle in nature: the biological equivalent of the laws of thermodynamics.

More than that, the ubiquity of kin altruism tells us something about the origins of our own nepotistic inclinations. No one would dream of explaining kin-directed altruism in Belding’s ground squirrels, American sea rocket, or bacterial moulds in terms of socialization or cultural norms. We explain it, without hesitation, in evolutionary terms. Is it plausible, then, when we find exactly the same pattern in our own species, to explain it in entirely different terms, as a pure product of learning or culture?

The short answer is no, it’s not plausible. It’s possible, I suppose. But in the absence of strong evidence that it’s actually the case, the default assumption should be that humans are continuous with the rest of nature and thus that our nepotistic streak has an evolutionary origin, just as it does for every other organism. The burden of proof falls squarely on the shoulders of the Nurture Only theorist.

And what a burden it is! Anyone who wants to deny that human kinship behaviour has anything to do with kin selection has an arduous task ahead of them. Here’s what they’ve got to do at a minimum:

1. They’ve got to explain why human beings are mysteriously exempt from a selection pressure that runs like an unbroken thread throughout the animal kingdom and all the way down to plants and bacteria.
2. They’ve got to explain why, at some point in our species’ past, kin altruism ceased to be adaptive for our species, and thus why selection wiped out the nepotistic streak that presumably existed in our pre-human ancestors.
3. They’ve got to explain why, despite this, people in every culture still manage to act in ways consistent with kin selection theory. Why would culture recapitulate biology in this way, given that kin altruism supposedly ceased to be adaptive in our lineage?

Kin selection theory is one of the great theories in the history of science. It places human beings within an explanatory framework that embraces the rest of the biological world – a framework that links suicidal nest-defence in bees and patterns of root growth in plants with the loving bonds and quiet self-sacrifice found in human families. I’m willing to go out on a limb and say that no psychologist or social scientist, who lacks a detailed understanding of kin selection theory, and an awareness of the importance of relatedness throughout the living world, can claim to be an expert on behaviour. Furthermore, any student of psychology or the social sciences who isn’t taught Hamilton’s ideas in some depth has been short-changed: They’ve missed out on one of the most profound theories of social behaviour yet to be proposed.

Natural selection making ‘education genes’ rarer, says Icelandic study




Epidemiological studies suggest that educational attainment is affected by genetic variants. Results from recent genetic studies allow us to construct a score from a person’s genotypes that captures a portion of this genetic component. Using data from Iceland that include a substantial fraction of the population we show that individuals with high scores tend to have fewer children, mainly because they have children later in life. Consequently, the average score has been decreasing over time in the population. The rate of decrease is small per generation but marked on an evolutionary timescale. Another important observation is that the association between the score and fertility remains highly significant after adjusting for the educational attainment of the individuals.


Epidemiological and genetic association studies show that genetics play an important role in the attainment of education. Here, we investigate the effect of this genetic component on the reproductive history of 109,120 Icelanders and the consequent impact on the gene pool over time. We show that an educational attainment polygenic score, POLYEDU, constructed from results of a recent study is associated with delayed reproduction (P < 10−100) and fewer children overall. The effect is stronger for women and remains highly significant after adjusting for educational attainment. Based on 129,808 Icelanders born between 1910 and 1990, we find that the average POLYEDU has been declining at a rate of ∼0.010 standard units per decade, which is substantial on an evolutionary timescale. Most importantly, because POLYEDU only captures a fraction of the overall underlying genetic component the latter could be declining at a rate that is two to three times faster.

Epidemiological studies have estimated that the genetic component of educational attainment can account for as much as 40% of the trait variance (1). Recent meta-analyses (23) yielded sequence variants contributing to the underlying genetic component. A negative correlation between educational attainment and number of children has been observed in many populations (47). A recent study of ∼20,000 genotyped Americans born between 1931 and 1953 provided direct evidence that the genetic propensity for educational attainment is associated with reduced fertility (89), supporting previously postulated notions (10) that the population average of the genetic propensity for educational attainment and related traits must be declining. Here, using a population-wide sample that is both much larger and covers a substantially greater time span, and with additional auxiliary information, we aim to estimate the change of the genetic propensity of educational attainment in the Icelandic population over the last few decades, starting with an in-depth investigation of the relationship between a measurable genetic component of educational attainment and various aspects of reproduction (1114).

Researchers say that while the effect corresponds to a small drop in IQ per decade, over centuries the impact could be profound

Spending longer in education and the career opportunities that provides is not the sole reason that better educated people tend to start families later and have fewer children, the study suggests. Many people who carried lots of genes for prolonged education left the system early and yet still had fewer children that the others. “It isn’t the case that education, or the career opportunities it provides, prevents you from having more children,” said Kari Stefansson, who led the study. “If you are genetically predisposed to have a lot of education, you are also predisposed to have fewer children.”

But the effect is very small. Writing in the Proceedings of the National Academy of Sciences the researchers estimate that it corresponds to a drop in IQ of about 0.04 points per decade. If all the genes that contribute to education were included, they add, that figure might rise to 0.3 points per decade. Nevertheless, Stefansson believes that if the trend continued for centuries, the impact could be serious.