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The Eoarchean quartz-pyroxene rock from Akilia Island in Greenland has been proposed as one of Earth’s oldest banded iron formations (BIF) and a potential host for the earliest biosignatures.

However, the origin of its protolith, whether it metamorphosed from an igneous or sedimentary precursor, remains debated. Here, we revisit this longstanding Akilia controversy using potassium isotope analyses, comparing Akilia samples with BIFs and black shales spanning the Eoarchean to Mesoproterozoic.

Our results demonstrate that BIFs and black shales show systematic potassium isotope variations correlated with their potassium contents. Potassium-poor BIF layers display heavier isotopic compositions close to seawater values, whereas clay-rich layers exhibit elevated potassium contents and lighter isotopic signatures.

The Akilia quartz-pyroxene rock was initially characterized by low potassium concentrations and heavy potassium isotopic compositions consistent with chemical sediments deposited from ancient seawater. It was subsequently modified by metasomatic fluids derived from nearby metamorphosed igneous rocks. These findings support a sedimentary origin for the Akilia quartz-pyroxene rock.

Furthermore, our study provides an isotopic framework for interpreting ancient oceanic environments and offers insights into the potassium cycling and habitability of early Earth.

Revisiting the Eoarchean Akilia quartz-pyroxene rock with potassium isotopes: Implications for early-ocean sedimentation, PNAS via PubMed

Astrobiology,

A team of international scientists has discovered new fossils at a field site in Africa that indicate Australopithecus and the oldest specimens of Homo coexisted at the same place in Africa at the same time — between 2.6 million and 2.8 million years ago. The paleoanthropologists discovered a new species of Australopithecus that has never been found anywhere. 

The Ledi-Geraru Research Project is led by scientists at Arizona State University, and the site has previously revealed the oldest member of the genus Homo and the earliest Oldowan stone tools on the planet.

The research team concluded that the Ledi-Geraru Australopithecus teeth are a new species, rather than belonging to Australopithecus afarensis (the famous “Lucy”), confirming that there is still no evidence of Lucy’s kind younger than 2.95 million years ago.

“This new research shows that the image many of us have in our minds of an ape to a Neanderthal to a modern human is not correct — evolution doesn’t work like that,” ASU paleoecologist Kaye Reed said. “Here we have two hominin species that are together. And human evolution is not linear — it’s a bushy tree; there are life forms that go extinct.” 

Reed is a research scientist at the Institute of Human Origins and President’s Professor Emeritus at the School of Human Evolution and Social Change at ASU. She has been co-director of the Ledi-Geraru Research Project since 2002.

Ledi-Geraru

What fossils did they find to help them tell this story? Teeth; 13 of them to be exact.

This field site has been famous before. In 2013, a team led by Reed discovered the jaw of the earliest Homo specimen ever found at 2.8 million years old. This new paper details new teeth found at the site that belong to both the genus Homo and a new species of the genus Australopithecus.

“The new finds of Homo teeth from 2.6- to 2.8-million-year-old sediments — reported in this paper — confirms the antiquity of our lineage,” said Brian Villmoare, lead author and ASU alumnus.

“We know what the teeth and mandible of the earliest Homo look like, but that’s it. This emphasizes the critical importance of finding additional fossils to understand the differences between Australopithecus and Homo, and potentially how they were able to overlap in the fossil record at the same location.”

The team cannot name the species yet based on the teeth alone; more fossils are needed before that can happen.

How old are the fossils?

How do scientists know these fossil teeth are millions of years old?

Volcanoes.

The Afar region is still an active rifting environment. There were a lot of volcanoes and tectonic activity, and when these volcanoes erupted ash, the ash contained crystals called feldspars that allow the scientists to date them, explained Christopher Campisano, a geologist at ASU. 

“We can date the eruptions that were happening on the landscape when they’re deposited,” said Campisano, a research scientist at the Institute of Human Origins and associate professor at the School of Human Evolution and Social Change.

“And we know that these fossils are interbed between those eruptions, so we can date units above and below the fossils. We are dating the volcanic ash of the eruptions that were happening while they were on the landscape.”

Finding fossils and dating the landscape not only helps scientists understand the species — it helps them re-create the environment millions of years ago. The modern faulted badlands of Ledi-Geraru, where the fossils were found, are a stark contrast to the landscape these hominins traversed 2.6 million to 2.8 million years ago. Back then, rivers migrated across a vegetated landscape into shallow lakes that expanded and contracted over time.

Ramon Arrowsmith, a geologist at ASU, has been working with the Ledi-Geraru Research Project since 2002. He explained the area has an interpretable geologic record with good age control for the geologic time range of 2.3 million to 2.95 million years ago.

“It is a critical time period for human evolution, as this new paper shows,” said Arrowsmith, professor at the School of Earth and Space Exploration. “The geology gives us the age and characteristics of the sedimentary deposits containing the fossils. It is essential for age control.”

What’s next?

Reed said the team is examining tooth enamel now to find out what they can about what these species were eating. There are still remaining questions the team will continue to work on.

Were the early Homo and this unidentified species of Australopithecus eating the same things? Were they fighting for or sharing resources? Did they pass each other daily? Who were the ancestors of these species?

No one knows — yet.

“Whenever you have an exciting discovery, if you’re a paleontologist, you always know that you need more information,” Reed said. “You need more fossils. That’s why it’s an important field to train people in and for people to go out and find their own sites and find places that we haven’t found fossils yet.

“More fossils will help us tell the story of what happened to our ancestors a long time ago — but because we’re the survivors, we know that it happened to us.”

The paper, “New discoveries of Australopithecus and Homo from Ledi-Geraru, Ethiopia,” was published in the journal Nature. The team of scientists and field team working on this project is widespread, and many work at Arizona State University or are alumni of ASU.

ASU alumni and current faculty authors include: University of Nevada, Las Vegas Associate Professor Brian Villmoare; University of Arkansas Associate Professor Lucas Delezene; Virginia Commonwealth University Professor Amy Rector; Penn State Associate Research Professor Erin DiMaggio; ASU Research Professor David Feary; ASU PhD candidate Daniel Chupik; Louisiana State University Instructor Dominique Garello; Idaho College of Osteopathic Medicine Assistant Professor Ellis M. Locke; Boston University Senior Lecturer Joshua Robinson; West Virginia School of Osteopathic Medicine Assistant Professor Irene Smail; and the late ASU Professor William Kimbel.

Below, Reed and Campisano talk more about this project in an in-depth interview.

There are many earthquakes in tectonically active mountains, so earthquake-induced landslides are a major component of erosion in these ranges. However, many factors influence the balance of uplift and erosion in mountains across the globe. Water and ice, rivers and glaciers, even plants and animals can cause erosion. The effects of earthquakes are nuanced as well. The magnitude of the quake, composition of the rock and dynamics of the watershed all affect the outcomes.

Li has begun investigating these details. He’s curious why the proportion of bedload in the Min River was so high after the 2008 earthquake. The bedload isn’t this high in all mountain rivers in seismically active regions, he explained. For instance, rivers in the Himalayas didn’t seem to experience such a high bedload flux after the 2015 Gorkha Earthquake in Nepal.

Answering this question requires studying the composition of the landslide material itself. Details like the kind of rock a mountain is made of can make an enormous difference in the number of landslides and size of debris, how sediment is transported and how quickly it flows downstream. Li’s team is working to combine data on grain size with advanced models describing how particles will behave as they travel down the watershed.

In science, answers always lead to more questions. And while the authors have their sights on solving a new set of quandaries, they’re quite proud of their contributions so far. As West said, “It’s very satisfying to have been able to quantify something that we’ve struggled to quantify before and that has a wide range of relevance, from hazards to long-term consequences for understanding the evolution of topography over long periods of time.”

About 5% of common Australian wild birds including kookaburras and lorikeets could have undergone a “sex reversal” where their genetic sex does not match their reproductive organs, according to a new study.

The study is thought to be the first to find widespread sex reversal across multiple wild bird species, but the cause of the phenomenon is not yet known.

The results suggest sex reversal is more common in wild birds than previously thought, and have raised concerns about the potential impact of chemicals that can disrupt hormones in animals.

Researchers tested 480 birds across five common species that had died after being admitted to wildlife hospitals in south-east Queensland.

Researchers first used a DNA test to determine a bird’s genetic sex; in birds, males have a pair of Z chromosomes and females have one Z and one W.

But after dissecting the birds, they found a mismatch between the DNA test and the reproductive organs of 24 of the birds.

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Associate Prof Dominique Potvin, a co-author of the research at the University of the Sunshine Coast, said the team were deeply sceptical when the results first came in.

“I was thinking, is this right?” she said. “So we rechecked, and rechecked and rechecked. And then we were thinking, ‘oh my God’.”

Potvin said she had revealed the results to ornithologist friends. “They were mind-blown,” she said.

Concern sex reversal may skew data

Almost all of the “sex discordant” birds were genetically female but had male reproductive organs, the research, published in the Royal Society journal Biology Letters found.

In one case, a kookaburra that was genetically male had a stretched oviduct – the passageway for an egg – that suggested “recent egg production”, Potvin said.

Two genetically female crested pigeons had both testicular and ovarian reproductive structures, the research found.

Other birds tested were rainbow lorikeets, scaly-breasted lorikeets and Australian magpies. The lowest levels of sex reversal was 3%, found in Australian magpies, and the highest was 6.3% in crested pigeons.

Dr Clancy Hall, the lead author of the research, also at the University of the Sunshine Coast, said sex-reversed birds could affect reproductive success that should raise concerns about the impact on threatened species.

She said: “This can lead to skewed sex ratios, reduced population sizes, altered mate preferences, and even population decline.

“The ability to unequivocally identify the sex and reproductive status of individuals is crucial across many fields of study.”

Experts say chemicals may be to blame

The causes of the sex reversals were unclear, but one factor could be contact with chemicals in the environment.

Sex reversal is known to occur in some molluscs, fish, amphibians and reptiles and can occur naturally or be influenced by chemicals that can affect an animal’s hormones – known as endocrine disrupting chemicals (EDCs).

Prof Kate Buchanan, who studies the evolutionary biology of wild birds at Deakin University but was not involved in the study, said because the default sex of birds was female, it was not surprising that most of the sex reversal affects were in the direction of female to male.

She said: “The most likely explanation of the masculinisation is some environmental stimulation, probably anthropogenic chemicals.”

Buchanan has been part of research that has found EDCs in insects that develop in sewage treatment works and are food for some birds, as well as a study that found male European starlings exposed to the chemicals developed longer and more complex songs, but had a damaged immune system.

She said even if the masculinisation of affected birds was reversible in their lifetime, “it would probably knock them out of being reproductive”.

Dr Clare Holleley is the head of vertebrate collections at the Australian government science agency the CSIRO and has studied sex reversal in lizards.

“What’s doing this is now the big question,” she said.

While a cause could be natural – for example, sex reversal in lizards can be triggered by temperature changes – Holleley said it was likely “something else is going on”.

“If sex determination gets disrupted then something has to push you off track. The most likely [cause] is endocrine disrupting chemicals.”

Dr Golo Maurer, the director of conservation strategy at BirdLife Australia, said the research was likely to cause a stir in the ornithological field.

He said the presence of EDCs and the potential impacts was a “huge concern”, given the other crises facing birds, from climate change to habitat clearance and plastic pollution.

Some experts were cautious about extrapolating the results to the wider population of wild birds, because the birds were not a random sample but had been admitted to hospitals.