Can plastic roads help save the planet?

Engineer Toby McCartney explains how his Scottish start-up MacRebur is persuading councils to use local waste plastic to build roads. Two English councils have already started building roads this way.

A smartphone film for BBC World Hacks by

Article source:


Brexit university ‘brain drain’ warning


Image caption

MPs say that universities need to have certainty about the future of EU staff and students

University staff from EU countries should be guaranteed a right to stay and work in the UK after Brexit to avoid a “damaging brain drain”, says a report from MPs.

The education select committee wants urgent steps taken to end uncertainty over the future status of EU academics.

The MPs also want overseas students to be taken out of migration figures.

Committee chairman Neil Carmichael said Brexit risks damaging universities’ “international competitiveness”.

About one in six academic staff in the UK is from EU countries.

The cross-party committee of MPs, investigating the potential impact of Brexit on the higher education sector, heard warnings about the negative impact if EU staff, worried about their future status, were poached by universities in other countries.

The report from MPs said their right to work and stay should be given unilaterally before the end of this year if there is no reciprocal deal with other EU countries

Mr Carmichael said: “Higher education in the UK is a world leader but Brexit risks damaging our international competitiveness and the long-term success of our universities.

“The government must act urgently to address the uncertainty over EU staff and avert the risk of a damaging brain drain of talent from our shores.”

‘Light-touch controls’

The MPs highlighted the economic value of the UK’s higher education sector – quoting an estimate that it was worth £73bn per year and supported 750,000 jobs.

There are 127,000 students from EU countries currently at UK universities – and the report calls for “light-touch controls” after Brexit rather than barriers that would discourage students from applying.

The MPs say there should be a “system closely resembling freedom of movement”, rather than risk losing a share of the lucrative overseas student market.

And the committee has added its voice to calls for overseas students not to be counted in migration figures and targets for cutting immigration.

Image caption

Cambridge University warned of losing talented mathematicians from eastern Europe

Among the evidence given to the committee, Prof Catherine Barnard from the University of Cambridge said her university had seen a 14% drop in applications from EU students.

She had warned that it could mean the loss of talented mathematicians from eastern Europe who would take their skills elsewhere.

MPs were also told of the importance of universities remaining international and outward looking – with much research now based on international partnerships.

Pam Tatlow, chief executive of the MillionPlus group of new universities, said: “EU students are worth over £2bn to the UK economy and we wholeheartedly endorse the committee’s recommendation that the UK should seek to retain visa-free access for these students and for UK students studying in Europe post-Brexit.”

Universities UK, responding to the report, called for “clarity” on the future for European staff and students “as soon as possible”.

The Department for Education last week offered reassurance to the next wave of prospective applicants, announcing that EU students beginning courses in autumn 2018 would still be able to receive loans.

Article source:


Household food waste level ‘unacceptable’

BananasImage copyright

The level of household food waste in England is “unacceptable” and householders have a key role to play in reducing it, MPs have said.

The Environment, Food and Rural Affairs Committee said 7.3m tonnes of food was wasted in UK households in 2015.

The committee said shops should relax standards that prevent the sale of “wonky vegetables” to help cut waste.

And the next government should consider whether “best before” dates were needed, it said.

Committee chairman Neil Parish said: “One-third of food produced for human consumption is lost or wasted globally, and in the UK over £10bn worth of food is thrown away by households every year.

“Economically, food waste costs households hundreds of pounds a year and causes increased disposal costs to local authorities, pushing up council tax bills.

“Socially, it is a scandal that people are going hungry and using food banks when so much produce is being wasted.

“And environmentally, it is a disaster, because energy and resources are wasted in production only for the food to end up rotting in landfills where it produces methane – a potent climate-changing gas.”

Food waste costs the average person in the UK £200 per year, the report said.

The average household lost £470 a year because of avoidable food waste, while those with children lost £700, it said.

The report said about two-thirds of the potential reduction in UK food waste would need to come from action at a household level.

It said it would be “hugely challenging” to reduce food waste further and would require “a considerable investment of resource”.

In their report, Food Waste in England, the MPs said:

  • The incoming government should establish a national food waste target for England.
  • It should examine how lessons on food and avoiding waste could be incorporated into the curriculum.
  • Waste reduction body Wrap, a charity which helps people and businesses reduce waste, should have sufficient money from the government to maintain its efforts in raising awareness.
  • Food businesses and retailers over a certain size should be forced to separate food waste for collection.
  • Supermarkets should be required by the government to publish data on the amount of food they bin. The report commended Tesco for already doing so and Sainsbury’s for moving in the same direction.
  • Retailers should increase the amount of surplus food they give away to charities.
  • Retailers should improve their packaging by, for example, increasing resealable packets.
  • Retailers should make food storage instructions clearer on packaging.
  • The next government should work with restaurants on reducing waste by, for example, offering smaller portions, reducing the amount of sides, and encouraging the taking home of leftovers.

It also called for a review of whether “best before dates” were needed at all.

While “use by” dates refer to food safety, “best before” labels refer only to quality.

Foods will be safe to eat after the “best before” date, but may not be at their best.

The report said current date labelling was unnecessarily confusing, and guidance should be issued to the industry by the end of the year.

The report also highlighted the issue of suppliers’ food being rejected for cosmetic reasons.

It said up to a quarter of apples, up to a fifth of onions and up to about an eighth of potatoes were rejected by supermarkets on cosmetic grounds alone.

Article source:


Premature lambs kept alive in ‘plastic bag’ womb

One of the lambs in the studyImage copyright
Partridge, E. A. et al. / Nature Communications

Image caption

The premature lambs matured and grew a wool

Scientists have been able to keep premature lambs alive for weeks using an artificial womb that looks like a plastic bag.

It provides everything the foetus needs to continue growing and maturing, including a nutrient-rich blood supply and a protective sac of amniotic fluid.

The approach might one day help premature human babies have a better chance of survival, experts hope.

Human trials may be possible in a few years, according to researchers.

First, more tests in animals are needed to check it is safe enough to progress, the researchers say in the journal Nature Communications.

The Children’s Hospital of Philadelphia team insists it is not looking to replace mothers or extend the limits of viability – merely to find a better way to support babies who are born too early.

Currently, very premature infants, born at around 23 weeks of gestation, are placed in incubators and put on ventilators to help them breathe, but this can damage their lung development.

Plastic bag womb

The plastic “biobag” womb contains a mixture of warm water and added salts, similar to amniotic fluid, to support and protect the foetus.

This fluid is inhaled and swallowed by the growing foetus, as would normally happen in the womb. Gallons of the mixture are steadily flushed through the bag each day to ensure a continuous fresh supply.

The bagged lamb cannot get a supply of oxygen and nutrients from its mum via the placenta. Instead, it is connected to a special machine by its umbilical cord, which does the job.

The baby lamb’s heart does all the pumping work, sending “old, used” blood out to the machine to be replenished before it returns back to the body again.

The whole system is designed to closely mimic nature and buy the tiniest newborns a few weeks to develop their lungs and other organs.

Researcher Dr Emily Partridge explained: “The challenging age that we are trying to offset is that 23- to 24-week baby who is faced with such a challenge of adapting to life outside of the uterus on dry land, breathing air when they are not supposed to be there yet.”

In babies born preterm, the chance of survival at less than 23 weeks is close to zero, while at 23 weeks it is 15%, at 24 weeks 55% and at 25 weeks about 80%.

The premature lambs in the study, equivalent in age to 23-week-old human infants, appeared to develop normally in their bags.

They opened their eyes, grew a woolly coat and appeared comfortable living in their polyethylene homes.

After 28 days, when their lungs had matured enough, the lambs were released so they could start breathing air.

Shortly after, the lambs were then killed so the researchers could study their brains and organs in detail to see how well they had grown.

In later experiments, however, a few more bagged lambs were allowed to survive and were bottle-fed by the team.

“They appear to have normal development in all respects,” said lead investigator Dr Alan Flake.

There are still many potential problems to overcome, however.

There is a significant risk of infection, even though the biobag is sterile and sealed. Finding the right mix of nutrients and hormones to support a human baby will also be a challenge.

Even if the work can progress, it’s not clear how parents-to-be might feel about it.

Fellow researcher Dr Marcus Davey said: “We envisage the unit will look pretty much like a traditional incubator. It will have a lid and inside that warmed environment would be the baby inside the biobag.”

Prof Colin Duncan, professor of reproductive medicine and science at the University of Edinburgh, said: “This study is a very important step forward. There are still huge challenges to refine the technique, to make good results more consistent and eventually to compare outcomes with current neonatal intensive care strategies.

“This will require a lot of additional pre-clinical research and development and this treatment will not enter the clinic any time soon.”

Follow Michelle on Twitter

Article source:


Primitive human ‘lived much more recently’

Naledi SkeletonImage copyright
John Hawks

Image caption

Homo naledi has much in common with early forms of the genus Homo

A primitive type of human, once thought to be up to three million years old, actually lived much more recently, a study suggests.

The remains of 15 partial skeletons belonging to the species Homo naledi were described in 2015.

They were found deep in a cave system in South Africa by a team led by Lee Berger from Wits University.

In an interview, he now says the remains are probably just 200,000 to 300,000 years old.

Although its anatomy shares some similarities with modern people, other anatomical features of Homo naledi hark back to humans that lived in much earlier times – some two million years ago or more.

“These look like a primitive form of our own genus – Homo. It looks like it might be connected to early Homo erectus, or Homo habilis, Homo rudolfensis,” said Prof Berger’s colleague, John Hawks, from the University of Wisconsin.

Although some experts guessed that naledi could had lived relatively recently, in 2015, Prof Berger told BBC News that the remains could be up to three million years old.

New dating evidence places the species in a time period where Homo naledi could have overlapped with early examples of our own kind, Homo sapiens.

Prof Hawks told the BBC’s Inside Science radio programme: “They’re the age of Neanderthals in Europe, they’re the age of Denisovans in Asia, they’re the age of early modern humans in Africa. They’re part of this diversity in the world that’s there as our species was originating.”

“We have no idea what else is out there in Africa for us to find – for me that’s the big message. If this lineage, which looks like it originated two million years ago was still hanging around 200,000 years ago, then maybe that’s not the end of it. We haven’t found the last [Homo naledi], we’ve found one.”

The naledi remains were uncovered in 2013 inside a difficult-to-access chamber within the Rising Star cave system. At the time, Prof Berger said he believed the remains had been deposited in the chamber deliberately, perhaps over generations.

This idea, which would suggest that Homo naledi was capable of ritual behaviour, met with controversy because such practices are thought by some to be characteristic of human modernity.

Prof Hawks says that the team has since started exploring a second chamber.

“[The second] chamber has the remains of an additional three individuals, at least, including a really, really cool partial skeleton with a skull,” said Prof Hawks.

Researchers have already attempted to extract DNA from the remains to gain more information about naledi‘s place in the human evolutionary tree. However, they have not yet been successful.

“[The remains] are obviously at an age where we have every reason to think there might be some chance. The cave is relatively warm compared to the cold caves in northern Europe and Asia where we have really good DNA preservation,” said Prof Hawks.

A study outlining the dating evidence is due for publication in coming months.

Follow Paul on Twitter.

For more on the Homo naledi remains, Inside Science is broadcast on Thursday 27 April at 16:30 BST on BBC Radio 4.

Article source:


Trump executive order aims to allow Arctic drilling

Donald Trump holds up an executive order while people behind him clapImage copyright

Donald Trump has signed an executive order aimed at reducing restrictions on oil drilling in the Arctic and Atlantic in order to “unleash American energy”.

The US president said it would create “thousands and thousands” of jobs, despite a downturn in the oil market.

It could undo a ban put in place by Barack Obama in order to protect swathes of the ocean from development.

But Interior Secretary Ryan Zinke said the decision was better than being held hostage by “foreign entities”.

Getting rid of Mr Obama’s environmental protections was one of Mr Trump’s promises to voters while on the campaign trail.

As he signed the order, called the America-First Offshore Energy Strategy, Mr Trump said: “Our country’s blessed with incredible natural resources, including abundant offshore oil and natural gas reserves, but the federal government has kept 94% of these offshore areas closed for exploration and production.

“This deprives our country of potentially thousands and thousands of jobs and billions of dollars in wealth.”

The order instructs the US Department of Interior to come up with a new development plan for all federal waters off US coasts.

It is debatable how much income might be generated by a reversal of Mr Obama’s order. Worldwide prices for oil have dropped in recent years, with a review by news agency Reuters finding the amount of money oil companies spent in the central Gulf of Mexico’s annual lease sale dropped by more than 75% between 2012 and 2017.

Meanwhile, environmental groups have already said they will challenge Mr Trump.

David Jenkins, president of Conservatives for Responsible Stewardship, a non-profit conservation group, said: “The Trump administration’s hasty move today toward expanding offshore oil drilling … defies market realities and is as reckless as it is unnecessary.”

Article source:


Physics of throwing analysed by scientists

Hand holding paper aeroplaneImage copyright

Image caption

The act of throwing is more complex than you would expect

Scientists have calculated the optimal strategy for throwing something accurately – whether it’s a dart or a crumpled-up piece of paper.

US researchers say the slow-is-more-accurate rule generally applies.

In a series of calculations, they looked at the physics behind releasing a projectile with the human arm.

Their equations suggest a slow but accurate throw is the best strategy for getting a piece of paper into a nearby bin.

Lead researcher Madhusudhan Venkadesan, assistant professor of mechanical engineering and materials science at Yale University, said faster throws tend to be less accurate.

This is because the ball travels in a nearly straight line, so any errors in the angle at which the object is released tend to be amplified.

In slow and curved flight paths, small errors in the angle of release have little effect, he said.

“What we find is that almost the slowest arc is often the most accurate,” said Dr Venkadesan.

“We’ve compared these calculations to published data of people throwing into wastebaskets; we’ve compared it to a study in dart throwing.”

In sports such as basketball or darts, the strategy depends on conditions and the trade-off needed between speed and accuracy.

For example, experienced darts players throw overarm at about 5.5 metres per second, optimally releasing the dart 17 to 37 degrees before the arm becomes vertical.

On the cricket pitch, fielders are more likely to strike the wicket with a fast underarm throw.

And in basketball, the underhand free throw, nicknamed “the granny throw”, has a marginal advantage over overhand, despite almost disappearing from the game.

Accurate throwing is uniquely human – a skill relied upon by our ancient ancestors for hunting with spears or stone tools.

The researchers say monkeys also throw things, but they are really bad at it.

The study is published in the journal, Royal Society Open Science.

Follow Helen on Twitter.

Article source:


‘Fossil’ groundwater’s modern secret

Media captionJim Kirchner: “Fossil groundwater fell as rain when mastodons still roamed the Earth”

The world’s oldest and deepest waters are not immune from contamination, warn scientists.

It had been assumed that “fossil” reserves found hundreds of metres underground would be largely untouched by modern water sources.

But sampling from some 10,000 wells shows this not to be the case.

The new study reveals that about half of the deep groundwater has had contact with rains and snows that fell in the past 60 years.

And that means these ancient aquifers are also at some risk from pollution if waste and land management practices are defective.

It is an issue of significance because fossil waters are an important resource, providing drinking supplies and irrigation for billions of people across the globe.

The scientists presented their findings here in Vienna at the European Geosciences Union General Assembly. They have also published a report in the journal Nature Geoscience.

Image copyright
Richard Taylor

Image caption

We will become increasingly dependent on deeper, older groundwater if shallower, younger groundwater becomes depleted

The team tested the deep waters for the presence of two radioactive elements.

The first was carbon-14 which occurs naturally in the environment and is pulled out of the air by rain and snow. This precipitation will eventually percolate into deep soil pore-spaces and rock fractures.

Because carbon-14 decays relatively slowly, a very low count in water will indicate great antiquity. Scientists will use the term fossil in this context to mean water that last touched the atmosphere more than about 10,000 years ago.

The second radioisotope to be checked was tritium, a heavy form of hydrogen which, in contrast, decays very rapidly. It was put in the atmosphere by A-bomb tests in the 1950s/1960s, so its presence is a sign of water’s youth.

“What we’ve learnt from these two radioisotopes is two things,” explained team-member Jim Kirchner from the Swiss Federal Institute of Technology in Zurich.

“One is that more than half of groundwater under our feet is fossil groundwater. The second important finding is that of this fossil groundwater, the water that comes out of those wells also contains a component of modern groundwater in at least half of cases.

“That means the water we are pumping from these deep wells, from what we think are ancient aquifers, also can potentially contain modern contaminants, either because of mixing within the well itself as the water is brought up, or because of mixing within the aquifer,” he told BBC News.

Image copyright
Richard Taylor

Image caption

A deep, handpump well supplying freshwater in the Sundarbans of coastal Bangladesh

The study’s lead author, Scott Jasechko of the University of Calgary, Canada, added: “We’re using the analogy of grandkids visiting their grandparents.

“Imagine fossil groundwaters are the grandparents and that younger groundwaters are the grandkids.

“We’re finding that groundwater grandkids often visit groundwater grandparents deep underground, and, unfortunately, sometimes these grandkids have the flu.

“These young groundwaters may carry contaminants down with them, impacting deep groundwater once considered immune to modern contamination.”

The scientists say the issue of pollution also now needs to be considered alongside the oft-discussed concern over the sustainable use of groundwater.

The deeply buried ancient water is what it is because of the time taken to build up, and hydrologists have long warned that it should really be viewed as a kind of “credit card”, to be drawn on principally only in periods of major water stress, such as during a severe drought.

This case will continue to be made, but the new study now adds in the extra matter of contamination risk.

Image copyright
Mark Hughes

Image caption

Groundwater supports about 40% of the world’s irrigated agriculture

Article source:


DNA of extinct humans found in caves

Vindija Cave, CroatiaImage copyright
MPI For Evo Anthro / J. Krause

Image caption

The remains of Neanderthals had previously been found at Vindija Cave in Croatia

The DNA of extinct humans can be retrieved from sediments in caves – even in the absence of skeletal remains.

Researchers found the genetic material in sediment samples collected from seven archaeological sites.

The remains of ancient humans are often scarce, so the new findings could help scientists learn the identity of inhabitants at sites where only artefacts have been found.

The results are described in Science.

Antonio Rosas, a scientist at Spain’s Natural Science Museum in Madrid, said: “This work represents an enormous scientific breakthrough.

“We can now tell which species of hominid occupied a cave and on which particular stratigraphic level, even when no bone or skeletal remains are present.”

Image copyright

Image caption

The researchers also found the DNA of many animals – some of them extinct

“We know that several components of sediments can bind DNA,” said lead researcher Matthias Meyer of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany.

“We therefore decided to investigate whether hominin DNA may survive in sediments at archaeological sites known to have been occupied by ancient hominins.”

The team collaborated with researchers excavating at seven dig sites in Belgium, Croatia, France, Russia and Spain.

They collected sediment samples covering a time span from 14,000 to 550,000 years ago.

Image copyright

Image caption

Neanderthal DNA was retrieved from sediments in El Sidrón cave, northern Spain

Back in the lab, they fished out tiny fragments of mitochondrial DNA (mtDNA) – genetic material from the mitochondria, which act as the “powerhouses” of biological cells. Even sediment samples that had been stored at room temperature for years yielded DNA.

Dr Meyer and his team members were able to identify the DNA of various animals belonging to 12 mammalian families, including extinct species such as the woolly mammoth, woolly rhinoceros, cave bear and cave hyena.

The scientists looked specifically for DNA from ancient humans in the samples.

“From the preliminary results, we suspected that in most of our samples, DNA from other mammals was too abundant to detect small traces of human DNA,” said co-author Viviane Slon, from the Max Planck Institute in Leipzig, Germany.

“We then switched strategies and started targeting specifically DNA fragments of human origin.”

Image copyright

Image caption

DNA can be extracted even when the sediments have been stored at room temperature

The team members managed to retrieve DNA from Neanderthals in the cave sediments of four archaeological sites, including in layers where no human skeletal remains have been discovered.

In addition, they found new samples of Denisovan DNA in sediments from Denisova Cave in Russia.

“The technique could increase the sample size of the Neanderthal and Denisovan mitochondrial genomes, which until now were limited by the number of preserved remains,” co-author Spanish National Research Council scientist Carles Lalueza-Fox told the AFP news agency.

“And it will probably be possible to even recover substantial parts of nuclear genomes.”

Svante Pääbo, director of the Evolutionary Genetics department at the Max Planck Institute for Evolutionary Anthropology, commented: “By retrieving hominin DNA from sediments, we can detect the presence of hominin groups at sites and in areas where this cannot be achieved with other methods.

“This shows that DNA analyses of sediments are a very useful archaeological procedure, which may become routine in the future.”

Article source:


First Americans claim sparks controversy

Fossils and rocksImage copyright
San Diego Natural History Museum

Image caption

Purported stone tools can be seen alongside broken mastodon bones at the excavation site near San Diego

A study that claims humans reached the Americas 130,000 years ago – much earlier than previously suggested – has run into controversy.

Humans are thought to have arrived in the New World no earlier than 25,000 years ago, so the find would push back the first evidence of settlement by more than 100,000 years.

The conclusions rest on analysis of animal bones and tools from California.

But many experts contacted by the BBC said they doubted the claims.

Thomas Deméré, Steven Holen and colleagues examined material from the Cerutti Mastodon site near San Diego. The site was originally uncovered in 1992, during highway construction work. Possible stone tools were discovered alongside the smashed up remains of a mastodon (Mammut americanum) – an extinct relative of mammoths and living elephants.

The researchers behind the latest study were unable to carry out radiocarbon dating on the remains, so they used a technique called uranium-thorium dating on several bone fragments, coming up with a date of 130,000 years.

The team members found that some of the bones and teeth bore a characteristic breakage pattern known as spiral fracturing, considered to occur when the bone is fresh. Additionally, some of the bones showed typical signs of being smashed with hard objects.

Rocks found alongside the mastodon remains show signs of wear and being struck against other surfaces, the researchers say. They conclude that these represent hammerstones and anvils – two types of stone tool used by prehistoric cultures.

Image copyright
Tom Deméré, San Diego NHM

Image caption

This close-up of a mastodon thigh bone shows spiral fractures

Dr Deméré, curator of palaeontology at the San Diego Natural History Museum, said the totality of evidence at the site had led team members to the conclusion that “humans were processing [working on or breaking up] mastodon limb bones using hammerstones and anvils and that the processing occurred at the site of burial 130,000 years ago”.

Dr Holen, co-director of the Center for American Paleolithic Research in South Dakota, commented: “We have conducted two experiments breaking elephant bones with large rock hammers and anvils. We produced exactly the same kind of fracture patterns as we found on the Cerutti mastodon limb bones.”

He added: “We can eliminate all of the natural processes that break bones like this. These bones were not broken by carnivore chewing, or by other animals trampling on this bone… the distribution patterns of the fractured pieces of bone right around the anvils is fairly conclusive evidence because we see that experimentally also.”

It’s not entirely clear why early humans smashed up the mastodon bones.

“We have no evidence that this is a kill or butchery site, but what we do have evidence of is that people were here breaking up the limb bones of this mastodon, removing some of the big thick pieces – probably to make tools out of – and they may also have been extracting the marrow for food,” said Dr Holen.

If the team’s conclusions are correct, people could have reached the Americas from Asia via a land bridge across the Bering Strait. This bridge periodically emerged during cold periods – when ocean water was locked up as ice – and disappeared when the climate warmed again and sea levels rose.

The earliest widely accepted evidence for humans in the Americas dates to roughly 15,000 years ago. This is a field where fierce debate has raged over rolling back the ages of human occupation by one or two thousand years, let alone 100,000.

Image copyright
Tom Deméré, San Diego NHM

Image caption

A boulder from the Cerutti Mastodon site that could have been used as a hammerstone

Dr Deméré and colleagues are not the first scientists to posit much earlier dates for people settling in the Americas. What distinguishes the latest work is that it has been published in one of the most prestigious peer-reviewed science journals in the world – Nature.

However, other experts remain unconvinced by the new evidence. Prof Michael R Waters, from Texas AM University in College Station, described the new paper as “provocative”.

He told BBC News the study “purports to provide evidence of human occupation of the Americas some 115,000 years before the earliest well established evidence”.

Prof Waters explained: “I have no issues with the geological information – although I would like to know more about the broader geological context – and the likely age of the locality. However, I am sceptical of the evidence presented that humans interacted with the mastodon at the Cerutti Mastodon site.”

“To demonstrate such early occupation of the Americas requires the presence of unequivocal stone artefacts. There are no unequivocal stone tools associated with the bones… this site is likely just an interesting paleontological locality.”

Prof Tom Dillehay, from Vanderbilt University in Nashville, Tennessee, told BBC News the claim was not plausible.

Another authority on early American archaeology, Prof David Meltzer from Southern Methodist University in Dallas, Texas, said: “Nature is mischievous and can break bones and modify stones in a myriad of ways.

Image copyright
Kate Johnson, San Diego NHM

Image caption

Experimental breakage was able to re-produce the same patterns seen at the ancient site

“With evidence as inherently ambiguous as the broken bones and non-descript broken stones described in the paper, it is not enough to demonstrate they could have been broken/modified by humans; one has to demonstrate they could not have been broken by nature.

“This is an equifinality problem: multiple processes can cause the same product.”

Chris Stringer, from London’s Natural History Museum, said that “if the results stand up to further scrutiny, this does indeed change everything we thought we knew about the earliest human occupation of the Americas,” adding: “If true, the results may well mean that archaic people like the Denisovans or Neanderthals were the first colonisers of the Americas, rather than modern humans.”

He explained that “extraordinary claims require extraordinary evidence – each aspect requires the strongest scrutiny,” but Prof Stringer also observed: “High and concentrated forces must have been required to smash the thickest mastodon bones, and the low energy depositional environment seemingly provides no obvious alternative to humans using the heavy cobbles found with the bones.”

The dating method used by the researchers to assign an age to this material works by measuring the radioactive decay of uranium that becomes incorporated into the bones over time.

“The type of samples that are most widely dated with this technique are ones that contain uranium as a primary substitution in their structure, such as inorganic carbonates, like cave carbonates, or corals, which take in uranium as they take calcium out of seawater,” Dr Warren D Sharp, an expert in isotope dating from the Berkeley Geochronology Center in California, told BBC News.

Image copyright
San Diego NHM

Image caption

The site was originally excavated during a highway expansion in the early 1990s

“What they’ve done in this paper is applied it to bone. That can be challenging because bones don’t contain significant amounts of primary uranium. They acquire the uranium when they become buried – they take it up from soil porewaters.”

He added: “That said, I think the dating is sound. They have done a very careful job. They have dated multiple samples and obtained similar results. The systematics of the concentrations of uranium in profiles across the bones are what you’d expect for reliable dates. And the bones that they’ve dated seem to be an integral part of the site, so their age should be relevant to the rest of the observations.”

Prof Meltzer said the history of the material from the site meant it would be difficult to prove that humans broke the bones. He explained: “[The evidence] comes from a site that was excavated [approximately] 25 years ago as a salvage project during a highway expansion.

“The kinds of detailed information necessary to understand how these bones and stones came to be… is simply not available. The authors do what they can with the extant collections, but they necessarily have to rely more on generalisations about what could (or could not) account for the evidence – which gets us back to the equifinality problem.”

Follow Paul on Twitter.

Article source:

© Warren Fyfe