Did human-like intelligence evolve to care for helpless babies?

baby
Credit: Anna Langova/public domain

A new study from the University of Rochester suggests that human intelligence might have evolved in response to the demands of caring for infants.

Steven Piantadosi and Celeste Kidd, assistant professors in brain and cognitive sciences, developed a novel evolutionary model in which the development of high levels of intelligence may be driven by the demands of raising offspring. Their study is available online in the Proceedings of the National Academy of Sciences' Early Edition.

"Human infants are born far more immature than the infants of other species. For example, giraffe calves are able to stand-up, walk around, and even flee from predators within hours of their births. By comparison, human infants cannot even support their own heads," said Kidd.

"Our theory is that there is a kind of self-reinforcing cycle where big brains lead to very premature offspring and premature offspring lead to parents having to have big brains. What our formal modeling work shows is that those dynamics can result in runaway pressure for extremely intelligent parents and extremely premature offspring," said Piantadosi.

In other words, because humans have relatively big brains, their infants must be born early in development while their heads are still small enough to insure a safe delivery. Early birth, though, means that human infants are helpless for much longer than other primates, and such vulnerable infants require intelligent parents. As a result, selective pressures for large brains and can become self-reinforcing—potentially creating species like humans with qualitatively different than other animals.

Piantadosi and Kidd tested a novel prediction of the model that the immaturity of newborns should be strongly related to general intelligence. "What we found is that weaning time—which acts as a measure of the prematurity of the —was a much better predictor of primate's intelligence than any of other measures we looked at, including brain size, which is commonly correlated with intelligence," said Piantadosi.

The theory may also be able to explain the origin of the cognitive abilities that make humans special. "Humans have a unique kind of intelligence. We are good at social reasoning and something called 'theory of mind'—the ability to anticipate the needs of others, and to recognize that those needs may not be the same as our own," said Kidd, who is also the director of the Rochester Baby Lab at the University of Rochester. "This is an especially helpful when taking care of an infant who is not able talk for a couple of years."

"There are alternative theories of why humans are so intelligent. A lot of these are based on factors like living in a harsh environment or hunting in groups," said Piantadosi. "One of the motivating puzzles of our research was thinking about those theories and trying to see why they predict specifically that primates or mammals should become so intelligent, instead of other species that faced similar pressures."

The key is live birth. According to the researchers, the runaway selection of intelligence requires both live birth of a single off spring and large brains, distinctive features of higher mammals.

"Our theory explains specifically why primates developed super intelligence but dinosaurs—who faced many of the same environmental pressures and had more time to do so—did not. Dinosaurs matured in eggs, so there was no linking between and infant immaturity at birth," said Kidd.


Explore further

New evidence reveals powerful role of experience in linking language and cognition in infants

More information: Extraordinary intelligence and the care of infants, PNAS, www.pnas.org/cgi/doi/10.1073/pnas.1506752113
Provided by University of Rochester
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May 23, 2016
Yeah which came first the chicken or the egg head?

Our brains were forced to grow due to enhanced competition among tribes in the context of technology.

Our tech enabled us to successively eliminate those natural attritive elements which served to keep our numbers in check. The result was unending conflict over resources. The tribe became the preferred social construct.

Those tribes whose members had better memories and were able to conceptualize, formulate, communicate, and execute complex battle strategies, and to develop and master more effective weapons, would win out in conflict.

And the victors would have eliminated all the enemy combatants and encorporated their females into their own tribe.

This unique form of group selection is what forced our brains to grow to their present unwieldy, unnatural, and unsustainable size.
Cont>

May 23, 2016
Females struggled to birth ever larger heads. They became more sedentary and their hips widened. Human babies are born premature and their heads continue to grow after birth. Their skulls remain pliable so they can distort while passing through the birth canal.

The demands for increased intelligence resulted in helpless babies, not the other way around.

May 23, 2016
Childbirth became the main cause of death for women, as it still is in many parts of the world today.

May 23, 2016
creating an UncleIra account to upvote yourself Ghost?

Anyway, addressing the article....

If live birth and large brains are the deciding factors then this is easily disputed. The walrus has a larger brain than a human, as do Blue whales and sperm whales. And perhaps whales more intelligent than us, but we have not tried hard to communicate with them.

So perhaps these are not the two most defining features of evolving intelligence.

May 23, 2016
In other words, because humans have relatively big brains, their infants must be born early in development while their heads are still small enough to insure a safe delivery.


That is a discredited theory. The real limit is the ability of the mother's metabolism to transfer oxygen to the developing baby, which limits the total birth size of the baby. At around 9 months time the metabolism of the growing baby exceeds the mother's ability to supply it internally, and it has to start breathing autonomously or the mother's body would start to get overstressed and the survival of both would be in jeopardy.

The question of brains then is how much of the amount of body mass at birth is dedicated to brain development and how much for the body.

May 23, 2016
The walrus has a larger brain than a human, as do Blue whales and sperm whales. And perhaps whales more intelligent than us, but we have not tried hard to communicate with them.


Brain size is linked with body mass because you need more nerve-endings for more muscles and larger organs. That's because a single nerve cell can only control so many muscle cells or connect to so many receptors: too much amplification of neural signals by branching off more neurons from a single nerve fiber results in low signal-to-noise ratio and jittery imprecise muscle control.

In other words, an animal with twice the muscle needs twice as many wires into the brain to move itself, and twice as many neurons in the cortex to fire to generate enough of a signal.

May 24, 2016
creating an UncleIra account to upvote yourself
I have more comments and related votes than most everybody here. My stats are impossible to move.
walrus brains, brains linked with body mass blah
Dinosaurs had relatively tiny brains. Human brains had to grow in order to extend memory and to be able to generate complex thoughts.

"chimpanzees, our closest living relatives, have brains that are one-third the size of our own, although they are very similar to us in body size. Most of this brain-size difference reflects the evolutionary expansion of the association cortex, a group of regions that supports such sophisticated cognitive functions as language, self-awareness, and problem solving."

-This includes imagining, conceptualizing, and synthesizing while drawing from experience as stored in memory.

Functionally our brains are unparalleled, but are structurally overextended. We are luckily smart enough to create superior brains designed from scratch.

May 24, 2016
because humans have relatively big brains, their infants must be born early in development while their heads are still small enough
That is a discredited theory. The real limit is the ability of the mother's metabolism to transfer oxygen
You didnt read the whole article youre referring to.

"Building on an idea previously put forth by study co-author Peter T. Ellison of Harvard University known as the metabolic crossover hypothesis, the team proposes that "energetic constraints of both mother and fetus are the primary determinants of gestation length and fetal growth in humans and across mammals."

-is what eikka is referring to. But

"Karen Rosenberg of U of Delaware, an expert on the evolution of human birth, what she thought about the new work, she called it "important and interesting." But "just because there's a metabolic moment when it becomes reasonable to have a baby doesn't mean it isn't also true that the pelvis is a tradeoff"
cont>

May 24, 2016
IOW an hypothesis is not a theory. Further it seems that the authors of that study are implying that the form factor of contemporary western women in their study is representative of women throughout our evolution. For instance

"the hypothesis predicts that because the female pelvis is broader than the male pelvis, walking and running should be more energetically demanding for women than for men. Yet most studies of the energetics and mechanics of locomotion in women and men found no such penalties for having a wider pelvis"

And

"Some women today have pelvic inlets that wide, and those larger dimensions have no measurable effect on locomotor cost"

-But people in the western world are a lot taller today than were those in the Pleistocene. And womens hips are narrower.

May 24, 2016
And perhaps whales more intelligent than us, but we have not tried hard to communicate with them
And I have seen no reports of whale cities or whale armies attacking commercial whaling ports. Or whales making their own harpoons.

What are you talking about? Whales have much greater incentive to talk to us than we to them.

May 25, 2016
Walruses may be one problem, intelligent birds another. Not human-like, but good at social reasoning and theory of mind (as recently demonstrated by ravens).

@Bart: Give it up, Empirical sciences do not live or die by not being 'mathematically ridiculous', whatever that means. Evolution is an observed fact. (Say, by you being different from your parents. These changes adds up in separated populations, c.f. how some people are lactase tolerant. Eventually the differences means speciation, see how we are nearly separated from Neanderthals. (Since their alleles are slowly going extinct, i.e. they didn't suit our subspecies environment.))

But as for math, the math of phylogenetic trees show that basic biology (evolution) is the best tested process description we have in all of science! [ http://www.talkor...comdesc/ ]

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