Humans

An analysis of fossils suggests changes in the shape of the braincase during human evolution were linked to alterations in the face, rather than changes in the brain itself

Humans

1 August 2022

By Luke Taylor
Digital restoration of child and adult crania from 160,000 years agoM. Ponce de León and Ch. Zollikofer/Univ. of Zurich
The physical transformation of the human cranium over the past 160,000 years was probably driven by alterations in the face resulting from diet and lifestyle changes, not from the evolution of the brain itself as previously thought, a study has found.
The cranium, or braincase, of early modern humans dating back 200,000 years isn’t much different in size from those today, but has a significantly different shape, suggesting that the brain has become rounder over time.
The leading hypothesis is that changes in behaviour, such as the development of tools and art, caused the shape of the Homo sapiens brain to change and, in turn, the skull that protects it.Advertisement
But fossil evidence is scarce and there are many interacting forces at play. It is simple for a skull with a large face to house a large brain, for example, but a small face complicates matters.
To investigate the causes behind the transformation of the braincase, Christoph Zollikofer at the University of Zurich in Switzerland and his colleagues digitally restored the skulls of 50 hominins recovered in Ethiopia and Israel, including H. sapiens as well as Homo erectus and Neanderthal specimens for comparison. The 3D models of the fossils were then compared with 125 modern human specimens.
Comparing the braincases of early modern human children with adults for the first time allowed the researchers to isolate the brain’s role in the evolution of the skull.
The team was surprised to find that while the size and proportions of the skulls of H. sapiens children from 160,000 years ago were largely comparable to infants today, the adults looked remarkably different to those of modern adults, with much longer faces and more pronounced features.

Human faces continue to grow until the age of around 20, but the brain reaches around 95 per cent of its adult size by age 6.
If the fossil children – with near fully developed brains – resemble living ones, but fossil adults had very different skulls, we can rule out that brains have changed significantly in shape, says Zollikofer. “And if it’s not the brain driving this change, we must look for something else, like breathing, eating or moving.”
The researchers cautiously hypothesise that changes in diet or a reduced need for oxygen could have been responsible.
Faces in modern humans are far smaller, with subtler indentation, than those of their ancestors. Studies show that this change accelerated when hunter-gatherers became agriculturalists around 12,000 years ago and ate softer foods, probably due to less loading on the skull from chewing.
The authors are right to remain cautious in their hypotheses, says Chris Stringer at the Natural History Museum in London.
There is little evidence of major dietary changes between the Middle and Late Stone Age when these changes occurred, he says. Of the many possible causes, a reduction in oxygen intake could be more likely as humans have developed smaller ribcages and have less lung capacity.
Journal reference: PNAS, DOI: 10.1073/pnas.2123553119
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Feedback raises an eyebrow at the cap which reads brainwaves to help China detect pornography, while also investigating secret cannabis facilities in Australia – and grave-robbing badgers

Humans

27 July 2022

Josie Ford
Thought police
Maintaining China’s 73-year ban on pornography is a job of work, but a natty new piece of headgear may help. The government’s “porn appraisers” have now merely to cast their eyes over suspect material at speed, and their caps – a sort of wire-covered shower cap developed by researchers at Beijing Jiaotong University – will read their brainwaves and detect when something catches their salacious interest. PC Gamer wonders why the system is so far only 80 per cent accurate, suspecting it is because the training material comes pre-censored. But what if the erroneous results were false positives? Feedback … More

Artificial turf has grown in popularity, but it has major drawbacks, says Beronda L. Montgomery, who is looking for a sustainable alternative

Humans

| Columnist

27 July 2022

By Beronda L. Montgomery
Olga Prava/Shutterstock
I RECENTLY stood surveying my new front lawn with a landscaper. The grass is a fine-bladed fescue variety that grows slowly, partly because it is a shade-tolerant species situated beneath the cover of my front yard’s large oak trees. These grasses are efficient at photosynthesis and can produce enough sugars to grow in limited light.
It is important to know whether your lawn is populated by sun-loving or shade-tolerant plants because they have different nutrient requirements. All plants have relatively high nitrogen needs because chlorophyll, which is central to photosynthesis, contains nitrogen. Shade-tolerant varieties, however, generally have lower nitrogen … More

This evolution bestseller is full of ironic humour, sharp insights and affectionate acknowledgement of human flaws – and ends up as a celebration of curiosity

Humans

27 July 2022

By Rebecca Wragg Sykes
Excavations at Atapuerca, near Burgos, Spain, shed new light on the first humans in Europeagefotostock/Alamy
Life As Told By a Sapiens to a Neanderthal
Juan José Millás and Juan Luis Arsuaga (translated by Thomas Bunstead and Daniel Hahn)
Scribe
IN THE Spanish city of Burgos, a towering 13th-century Gothic cathedral stands opposite the Museum of Human Evolution. Built 800 years apart, these buildings are both dedicated to finding meaning and exploring human origins, but the bones in the museum are 1000 times older than the cathedral, and its “high priest” … More

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Zero to Birth reveals how the brain is built, as neurobiologist William Harris explores the development of the human brain in utero and a bit beyond. Catch it live at the Royal Institution, London, at 7pm BST on 8 August.

Read
The Uses of Delusion are manifold, says psychologist Stuart Vyse. In this new book, he connects research into illogical thinking with its evolutionary origins and explains the possible benefits of irrational behaviour. On sale from 1 August.

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The Sandman stars Tom Sturridge as the titular lord of dreams, imprisoned by … More

In Emmi Itäranta’s The Moonday Letters, humans have adapted to live off-world. But central to this genre-crashing thrill ride is a reminder that hope is essential

Humans

27 July 2022

By Sally Adee

Living off-world is the norm in Emmi Itäranta’s new sci-fi novelGorodenkoff/Getty Images
The Moonday Letters
Emmi Itäranta
Titan

THE culture on Europa is so different from anywhere else in the solar system that visitors need to be carefully briefed during the inbound journey.

The settlements established on the Jovian moon – domes built in the ocean deep beneath its frozen surface – are shielded from the harsh radiation of space by a thick crust of ice. A crack anywhere would be devastating and the ice is sensitive to sound, … More

Shutterstock/Bangkok Click Studio
I AM a science teacher and I think anyone who spends time with young children can be one too. It is in the home that children first encounter literature, maths, music and art – through reading, counting, singing and drawing. But this sort of informal teaching isn’t so common when it comes to science. That is partly because many people lack the knowledge or confidence to talk about science with children, and partly because science isn’t ingrained in our culture in quite the same way.
Some children do try out “experiments” at home, such as making a “volcano” using bicarbonate of … More

Archaeological and genetic evidence casts doubt on the idea that the ability to digest lactose after infancy evolved gradually

Humans

27 July 2022

By Luke Taylor
Neolithic people began drinking milk around 7000 BCCHRISTIAN JEGOU/SCIENCE PHOTO LIBRARY
Milk consumption was widespread thousands of years before people were able to break it down properly, according to the largest study yet on the evolution of lactose tolerance in humans. The ability to break down lactose was probably gained during episodes of acute crisis, not gradually over time, the study found.
As babies, all humans produce the enzyme lactase, which breaks down lactose into the more readily absorbed glucose and galactose, but many people have much lower levels of lactase after weaning, meaning they cannot digest milk properly.
The spread of lactase persistence – the ability to break down lactose after weaning – is considered one of the best examples of natural selection in humans. One-third of the global population gained this trait in just a couple of thousand years.Advertisement
The leading explanation was that humans gained lactase persistence so quickly as their evolution was deeply intertwined in a cycle with dairy. As humans were pressured into evolving lactase persistence due to the nutritional benefits of milk, the spread of lactase persistence would have in turn increased human reliance on milk, increasing the pressure to be lactose tolerant.
Richard Evershed at the University of Bristol, UK, and his colleagues studied 7000 animal fat residues that had seeped into pottery at 500 sites across Europe. This revealed that dairy farming was common in the region from 7000 BC onwards.
But ancient DNA evidence revealed that lactase persistence wasn’t prevalent until around 1000 BC — roughly 4000 years after the trait was first detected and 6000 years after milk production took hold.
There are many ideas as to why lactose tolerance developed so rapidly, ranging from the benefits of milk’s sugar content to vitamin D, but they “all go out the window because they are all pinned to milk use in one way or another”, Mark Thomas of University College London, a co-author of the study, told a press briefing.
Mapping the use of milk across Europe against the spread of lactase persistence showed no correlation, while computer models suggest that famine and disease offer better explanations.
Using changes in population size as a proxy for malnutrition, the researchers found lack of food was 689 times more likely to explain the rise of lactose tolerance than constant selection pressure. Using population density as a proxy for the spread of deadly pathogens, they found that disease was 289 times more likely to account for the spread.
During these periods of crisis, the flatulence, stomach cramps or diarrhoea experienced by lactose intolerant people probably turned into a life or death matter, said Thomas.

An analysis of health and genetic data from the UK Biobank also suggested that the co-evolution idea for humans and lactose tolerance is unlikely.
Lactose tolerant people would be expected to have higher levels of some health metrics, such as bone mineral density, height or vitamin D, Thomas said, but the researchers found none except for slightly higher body mass index numbers.
Surprisingly, there was also little difference in the proportion of people who don’t drink cow’s milk amongst the lactose tolerant and intolerant: 6.8 per cent versus 8 per cent.
The results suggest that many people should consider drinking milk for its nutritional benefits, even if they are lactose intolerant, Evershed said at the briefing. “Broadly, if you’re lactose non-persistent it isn’t necessarily such a big deal.”
The negative symptoms associated with milk consumption only occur in some people who are lactose intolerant, probably due to variations in bacteria in the colon. Some people who experience side effects may be confounding lactose intolerance with milk allergy, the researchers said.
Journal reference: Nature, DOI: 10.1038/s41586-022-05010-7
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