Earth was momentarily ripe for the evolution of animals hundreds of millions of years before they first appeared, researchers propose.

Chemical clues in ancient rocks suggest that 2.32 billion to 2.1 billion years ago, shallow coastal waters held enough oxygen to support oxygen-hungry life-forms including some animals, researchers report the week of January 16 in the Proceedings of the National Academy of Sciences. But the first animal fossils, sponges, don’t appear until around 650 million years ago, following a period of scant oxygen known as the boring billion (SN: 11/14/15, p. 18).
“As far as environmental conditions were concerned, things were favorable for this evolutionary step to happen,” says study coauthor Andrey Bekker, a sedimentary geologist at the University of California, Riverside. Something else must have stalled the rise of animals, he says.

Microbes began flooding Earth with oxygen around 2.3 billion years ago during the Great Oxidation Event. This breath of oxygen enabled the eventual emergence of complex, oxygen-dependent life-forms called eukaryotes, an evolutionary line that would later include animals and plants. Scientists have proposed that the Great Oxidation Event wasn’t a smooth rise, but contained an “overshoot” during which oxygen concentrations momentarily peaked before dropping to a lower, stable level during the boring billion. Whether that overshoot was enough to support animals was unclear, though.

Bekker and colleagues tackled this question using a relatively new way to measure ancient oxygen. Rock weathering can wash the element selenium into the oceans. In oxygen-free waters, all of the selenium settles onto the seafloor. But in water with at least some oxygen, only a fraction of the selenium is deposited. And the selenium that is laid down is disproportionately that of a lighter isotope of the element, leaving atoms of a heavier isotope to be deposited elsewhere.
If ancient coasts contained relatively abundant oxygen, the researchers expected to find more light selenium close to shore and more heavy selenium in deeper, oxygen-deprived waters. Analyzing shales formed under deep waters around the world, the researchers found just such an isotope segregation. These shales had an abundance of the heavier selenium, leading researchers to infer that the lighter version of the element was concentrated closer to shore.

Oxygen concentrations in coastal waters were at least nearly one percent of present-day levels and “were flirting with the limits of what complex life can survive,” proposes study coauthor Michael Kipp, a geochemist at the University of Washington in Seattle. While the environment was probably suitable for eukaryotes, life hadn’t evolved enough by this point to take advantage of the situation, Kipp proposes. The appearance of eukaryotes in the fossil record would take hundreds of millions of years of more evolution (SN Online: 5/18/16), he says, and the first animals even longer.
Tracking selenium is such a new technique, though, that “interpretations could change as we better understand how it works,” says Philip Pogge von Strandmann, a geochemist at University College London. Currently the method is “tricky,” he says, especially for precisely estimating oxygen concentrations.

Legos have provided the inspiration for small, fluid-ferrying devices that can be built up brick-by-brick.

Tools for manipulating tiny amounts of liquid, known as microfluidic devices, can be used to perform blood tests, detect contaminants in water or simulate biological features like human blood vessels. The devices are easily portable, about the size of a quarter and require only small samples of liquid.

But fabricating such devices is not easy. Each new application requires a different configuration of twisty little passages, demanding a brand new design that must be molded or 3-D printed.

Scientists from the University of California, Irvine created Lego-style blocks out of a polymer called PDMS. Their bricks contained minuscule channels, half a millimeter wide, that allowed liquid to flow from brick to brick with no leaks. New devices could be created quickly by rearranging standard blocks into various configurations, the scientists report January 24 in the Journal of Micromechanics and Microengineering.

Gender bias works in subtle ways, even in the scientific process. The latest illustration of that: Scientists recommend women less often than men as reviewers for scientific papers, a new analysis shows. That seemingly minor oversight is yet another missed opportunity for women that might end up having an impact on hiring, promotions and more.

Peer review is one of the bricks in the foundation supporting science. A researcher’s results don’t get published in a journal until they successfully pass through a gauntlet of scientific peers, who scrutinize the paper for faulty findings, gaps in logic or less-than-meticulous methods. The scientist submitting the paper gets to suggest names for those potential reviewers. Scientific journal editors may contact some of the recommended scientists, and then reach out to a few more.

But peer review isn’t just about the paper (and scientist) being examined. Being the one doing the reviewing “has a number of really positive benefits,” says Brooks Hanson, an earth scientist and director of publications at the American Geophysical Union in Washington, D.C. “You read papers differently as a reviewer than you do as a reader or author. You look at issues differently. It’s a learning experience in how to write papers and how to present research.”

Serving as a peer reviewer can also be a networking tool for scientific collaborations, as reviewers seek out authors whose work they admired. And of course, scientists put the journals they review for on their resumes when they apply for faculty positions, research grants and awards.

But Hanson didn’t really think of looking at who got invited to be peer reviewers until Marcia McNutt, a geophysicist and then editor in chief of Science, stopped by his office. McNutt — now president of the National Academy of Sciences in Washington, D.C. — was organizing a conference on gender bias, and asked if Hanson might be able to get any data. The American Geophysical Union is a membership organization for scientists in Earth and space sciences, and it publishes 20 scientific journals. If Hanson could associate the gender and age of the members with the papers they authored and edited, he might be able to see if there was gender bias in who got picked for peer review.

“We were skeptical at first,” he says. Hanson knew AGU had data for who reviewed and submitted papers to the journals, as well as data for AGU members. But he was unsure how well the two datasets would match up. To find out, he turned to Jory Lerback, who was then a data analyst with AGU. Merging the datasets of all the scientific articles submitted to AGU journals from 2012 to 2015 gave Lerback and Hanson a total of 24,368 paper authors and 62,552 peer reviews performed by 14,919 reviewers. For those papers, they had 97,083 author-named reviewer suggestions, and 118,873 editor-named reviewer requests.

While women were authors less often and submitted fewer papers, their papers were accepted 61 percent of the time. Male authors had papers accepted 57 percent of the time. “We were surprised by that,” Hanson says. While one reviewer of Hanson and Lerback’s analysis (a peer-reviewer on a paper about peer review surely must feel the irony) suggested that women might be getting higher acceptance rates due to reverse discrimination, Hanson disagrees. He wonders if “[women] are putting more care into the submission of the papers,” he says. Men might be more inclined to take more risks, possibly submitting papers to a journal that is beyond their work’s reach. Women, he says, might be more cautious.
When suggesting reviewers, male authors suggested female reviewers only 15 percent of the time, and male editors suggested women just 17 percent of the time. Female authors suggested women reviewers 21 percent of the time, and female editors suggested them 22 percent of the time. The result? Women made up only 20 percent of reviewers, even though 28 percent of AGU members are women and 27 percent of the published first authors in the study were women.

The Earth and space sciences have historically had far fewer women than men, but the numbers are improving for younger scientists. “We thought maybe people were just asking older people to review papers,” says Lerback. But when Lerback and Hanson broke out the results by age, they saw the gender discrepancy knew no age bracket. “It makes us more confident that this is a real issue and not just an age-related phenomenon,” Lerback says. She and Hanson report their analysis in a comment piece in the January 26 Nature.

“It’s incredibly compelling data and one of those ‘why hasn’t someone done this already’ studies,” says Jessi Smith, a social psychologist at Montana State University in Bozeman. While it’s disheartening to see yet another area of bias against women, she notes, “this is good that people are asking these questions and taking a hard look. We can’t solve it if we don’t know about it.”

The time when authors are asked to suggest reviewers might play a role, Smith notes. When scientific papers are submitted online, the field for “suggested reviewers” is often last. “That question for ‘who do you want’ always surprises me,” admits Smith. It’s a very small thing, but she notes that when people are tired and in a hurry, “that’s when these biases take place.”

Knowing that the bias exists is part of the battle, Hanson says, but it’s also time for things to change. He’s pushing for more diversity in the journals’ editorial pool — for gender, nationality and underrepresented minorities. It’s also helpful to remember that suggesting people for peer review isn’t just about the author’s work. “Even small biases, if they happen repeatedly, can have career-related effects,” he says.

Peer-reviewer selection is something that hasn’t gotten a lot of scientific attention. “I think getting a dialog going for everyone to be aware of opportunity gaps, [asking] ‘what can I do to make sure I’m not contributing to this’… I think that will be important to keep editors and authors aware and accountable,” Lerbeck says. She’s now experiencing the peer-review life first hand: She’s now a graduate student at the University of Utah in Salt Lake City. While there, she’s starting a group to discuss bias — to make sure that the conversations keep going.

Physical abuse at home doesn’t just leave kids black and blue. It also bruises their ability to learn how to act at school and elsewhere, contributing to abused children’s well-documented behavior problems.

Derailment of a basic form of social learning has, for the first time, been linked to these children’s misbehavior years down the line, psychologist Jamie Hanson of the University of Pittsburgh and colleagues report February 3 in the Journal of Child Psychology and Psychiatry. Experiments indicate that physically abused kids lag behind their nonabused peers when it comes to learning to make choices that consistently lead to a reward, even after many trials.
“Physically abused kids fail to adjust flexibly to new behavioral rules in contexts outside their families,” says coauthor Seth Pollak, a psychologist at the University of Wisconsin–Madison. Youth who have endured hitting, choking and other bodily assaults by their parents view the world as a place where hugs and other gratifying responses to good behavior occur inconsistently, if at all. So these youngsters stick to what they learned early in life from volatile parents — rewards are rare and unpredictable, but punishment is always imminent. Kids armed with this expectation of futility end up fighting peers on the playground and antagonizing teachers, Pollak says.

If the new finding holds up, it could lead to new educational interventions for physically abused youth, such as training in how to distinguish safe from dangerous settings and in how to control impulses, Pollak says. Current treatments focus on helping abused children feel safe and less anxious.

More than 117,000 U.S. children were victims of documented physical abuse in 2015, the latest year for which data are available.

“Inflexible reward learning is one of many possible pathways from child maltreatment to later behavior problems,” says Stanford University psychologist Kathryn Humphreys, who did not participate in the new study. Other possible influences on physically abused kids’ disruptive acts include a heightened sensitivity to social stress and a conviction that others always have bad intentions, Humphreys suggests.

Hanson’s team studied 41 physically abused and 40 nonabused kids, ages 12 to 17. Participants came from various racial backgrounds and lived with their parents in poor or lower middle-class neighborhoods. All the youth displayed comparable intelligence and school achievement.
In one experiment, kids saw a picture of a bell or a bottle and were told to choose one to earn points to trade in for toys. Kids who accumulated enough points could select any of several desirable toys displayed in the lab, including a chemistry set and a glow-in-the-dark model of the solar system. Fewer points enabled kids to choose plainer toys, such as a Frisbee or colored pencils.

Over 100 trials, one picture chosen at random by the researchers at the start of the experiment resulted in points 80 percent of the time. The other picture yielded points 20 percent of the time. In a second round of 100 trials using pictures of a bolt and a button, one randomly chosen image resulted in points 70 percent of the time versus 30 percent for the other image.

Both groups chose higher-point images more often as trials progressed, indicating that all kids gradually learned images’ values. But physically abused kids lagged behind: They chose the more-rewarding image on an average of 131 out of 200 trials, compared with 154 out of 200 trials for nonabused youth. The abused kids were held back by what they had learned at home, Pollak suspects.