Ancient Comets May Have Delivered Xenon To Earth

<section class="entry-content instapaper_body clearfix" itemprop="articleBody">
<div class="add-container clearfix" id="add-block-placer">
</div>
<p>
  Comets hurtling through space 3.5–4.5 billion years ago may have deposited heavy isotopes of xenon into Earth’s atmosphere. This clue to the isotopes’ mysterious origins suggests that comets visited Earth in its earliest days, that the moon and atmosphere are younger than we originally thought, and that comets might have delivered the first organic material to our fledgeling planet.
 </p>
<p>
  While there are only trace amounts of xenon in the atmosphere, the noble gas doesn’t chemically react with other elements, meaning it’s
  <a href="http://www.spacedaily.com/reports/Rosetta_finds_comet_connection_to_Earths_atmosphere_999.html">
   a relatively stable marker
  </a>
  whose origin is easy to trace.
 </p>
<figure class="richtext-image full-width">
<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/crescent_comet_67p.width-990_sV88K8o.jpg"/>
<figcaption>Comet 67P/Churyumov-Gerasimenko
        
    </figcaption>
</figure>
<p>
  But the presence of a surprisingly high percentage of heavy xenon isotopes in Earth’s atmosphere has hampered our understanding of our planet’s origins. Scientists previously couldn’t find any plausible sources for these heavier isotopes—solar wind and meteors, for example, only contain lighter isotopes.
 </p>
<p>
  The new data comes from gas collected during the
  <a href="http://sci.esa.int/rosetta/">
   Rosetta mission
  </a>
  , which flew a spacecraft near the surface of 67P/Churyumov-Gerasimenko, a member of the family of comets controlled by Jupiter’s gravity. The samples contained a mixture of three noble gases, krypton, argon, and xenon. This comet’s xenon contained the same perplexing heavy isotopes, suggesting that Earth may have received a fraction of its xenon from comets. The model that best fits the atmosphere’s xenon makeup estimates that about 22% of it came from comets.
 </p>
<p>
  These
  <a href="http://science.sciencemag.org/content/356/6342/1069">
   new findings
  </a>
  allow scientist to correct small errors in dating the planet’s evolution. Here’s Leah Crane for
  <a href="https://www.newscientist.com/article/2134120-the-mystery-xenon-in-earths-atmosphere-came-from-icy-comets/">
   New Scientist
  </a>
  :
 </p>
<blockquote>
<p>
   On Earth, we presumed the presence of this isotope was primarily a result of decaying iodine. We know the rate at which iodine decays, so we use the quantity of xenon-129 to gauge the time at which planetary events took place. But if 22 per cent of the xenon in Earth’s atmosphere was transported by comets, models based on iodine decay aren’t accurate. They overestimate the age of Earth’s atmosphere and the moon.
  </p>
</blockquote>
<p>
  Since this study only examines data from one comet, missions to other comets will need to verify the results. But this cometary xenon further links Earth’s birth with the rest of the solar system. Results from other comets will provide further details of Earth’s formative years and perhaps even an explanation for how the first organic molecules arrived on Earth.
 </p>
</section>
<p>
 Image Credit: Giuseppe Conzo/ESA/Rosetta/NAVCAM
</p>

New Fossils Push Back Earliest Single-Celled Skeletons 200 Million Years

<div class="related"></div>
<p>
</p>
<p>
 Imagine trying to eat food without teeth, or walk without a backbone.
</p>
<p>
 While the single-celled organisms that dominated early Earth’s oceans didn’t have much need for teeth, they did find some evolutionary advantage in making their own minerals. According to research published last week, life has been making its own hard parts for at least 810 million years, about 200 million years longer than previously thought. It’s the first occurrence of what scientists call biomineralization, and it could give us deeper insight into both the evolution of living things and Earth’s early climate.
</p>
<p>
 Previously, scientists hadn’t found evidence of organisms making their own skeletons before the rapid diversification of life around 490-550 million years ago known as the Cambrian explosion. But in the mid-2000s, Phoebe Cohen, a Williams College paleontologist and lead author of the recent study, re-examined fossil evidence that would end up setting the date back much further.
</p>
<p>
 Cohen was in the Yukon studying microfossils from a 200-foot-thick section of lime, mudstone, and slate, and she suspected that they could have been formed by biological processes. These microfossils were originally discovered in the 1980s, when they were dated to the Neoproterozoic Era, about 250 million years prior to the Cambrian explosion. But scientists at the time were unable to determine the exact age of the fossils, nor were they able to discern whether they were crafted by geology or life itself.
</p>
<div class="ad"></div>
<p>
 To unlock the minerals’ secrets, Cohen and her co-author Nicholas Tosca borrowed a method of microscopic imaging from materials scientists that uses electrons instead of light. That imaging revealed highly organized, long, and slender crystals that were oriented and spaced in such a way that they could only have been made biologically, Cohen said.
</p>
<p>
 The minerals possibly served as an armor-like casing constructed by now-extinct organisms, though Cohen and her team did not find conclusive evidence of their function, nor did they find remnants of the cells themselves, which rarely preserve for so long. Cohen said these parts could have been a defense against a predation, since some single-celled organisms today use hard parts for protection. Plus, evidence in the fossil record suggests that predatory single-celled organisms would have existed at the same time as Cohen’s fossils.
</p>
<p>
 Shuhai Xiao, a paleobiologist at Virginia Tech who did not contribute to the paper, said it’s a reasonable hypothesis. “Organisms don’t make something just because there is material available,” Xiao said. “There must also be an ecological need.”
</p>
<p>
 Cohen and Tosca’s research cleverly uses “the way a mineral is constructed” to determine its origin, said Sara Pruss, a Smith College geologist who did not contribute to this study. It’s the first study to use a detailed analysis of crystal structure to find evidence of biomineralization. The same technique could be used to find other biomineralization from the same era in other parts of the world.
</p>
<p>
 The analysis also revealed that the minerals were composed of a particular flavor of phosphorus called hydroxylapatite, which is rarely found in oceanic single-celled organisms today. Cohen and her team found evidence in the rocks suggesting that the oceans at the time contained less oxygen than today. This provided a suitable environment for elevated phosphorus concentrations, which may have helped spur its use in biomineralization.
</p>
<p>
 “Hydroxylapatite is not very stable, so the preservation of the mineral in rocks of this age is remarkable,” Xiao said.
</p>
<p>
 The team was able to constrain the age of the fossils to an unusually narrow time-frame – 810 million years ago, give or take about 6 million years. As a result, Cohen thinks she’ll be able to find more fossils because she will only have to search a much narrower slice of the fossil record than before. “I was looking through a hundred million years of time before, and now I’m looking through ten million years,” she said.
</p>
<p>
 The new study leaves a few questions unanswered, and poses a few new ones of its own. For one, biomineralization has evolved several different times. This study illustrates how one branch of life gained the ability to make skeletal parts, but there are still several others to puzzle out. And then it blasts open a period of more than 200 million years in which scientists so far have found no evidence of biomineralization, a range of time that Cohen points out is as wide as that between the present day and the dawn of the dinosaurs.
</p>
<p>
 “We’re seeing a little bit of a mystery there,” Cohen said of the gap. They will now try to pinpoint when the shift from using phosphorus to using carbon occurred and find out what, if anything, organisms were making during that time. “That’s the big open question,” Cohen said.
</p>
<div class="newsletter"></div>
<p>
 Photo credit: Phoebe A. Cohen
</p>

<p>These 810 million-year-old fossils suggest early marine life protected itself by making skeletons from phosphorus.</p>

Early Brain Scans Could Predict Likelihood of Autism Diagnosis

<section class="entry-content instapaper_body clearfix" itemprop="articleBody">
<div class="add-container clearfix" id="add-block-placer">
</div>
<p>
  Doctors typically diagnose Autism Spectrum Disorder (ASD) at around age four by evaluating behaviors that start to develop at age two. But infants at high risk of autism can now get a brain scan to accurately predict the likelihood of diagnosis, according to
  <a href="http://stm.sciencemag.org/content/9/393/eaag2882">
   a new study
  </a>
  .
 </p>
<p>
  Researchers from the University of North Carolina at Chapel Hill examined functioning magnetic resonance imaging (fMRI) brain scans and behavioral tendencies of 59 six-month-olds who had older siblings on the autism spectrum.
 </p>
<p>
  They collected similar information when the children were two, then fed all of this material into a machine-learning algorithm that looked for correlations between the scanned data and behavioral data. The computer used the brain scans to predict whether the child would later be diagnosed with autism. It caught 9 of the 11 cases and produced no false positives (a result that indicates that a condition is present when, in fact, it is not).
 </p>
<figure class="richtext-image full-width">
<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/autism-brain-scans.width-990_IRJFjar.jpg"/>
<figcaption>Schematics representing brain scan signatures that predicted later autism diagnosis in infants.
        
    </figcaption>
</figure>
<p>
  However, there is still a dilemma of whether
  <a href="http://www.pbs.org/wgbh/nova/next/body/autism-early-intervention/">
   early behavioral intervention
  </a>
  for those diagnosed with ASD is ethical. Here’s Anil Ananthaswamy,
  <a href="https://www.newscientist.com/article/2133941-baby-brain-scans-can-predict-who-is-likely-to-develop-autism/">
   reporting
  </a>
  for New Scientist:
 </p>
<blockquote>
<p>
   Many people consider autism to be a fundamental part of their personality, and although some autistic people have substantial difficulty communicating or forming relationships, some people with autism value traits such as abilities to concentrate, pay attention to detail or see things from a novel perspective.
  </p>
</blockquote>
<p>
  Behavioral therapy might be less controversial if future research were to link brain functioning to specific behaviors. This would allow for treatment targeted at detrimental behaviors and in general would improve the treatment’s efficacy. Further research, beyond replicating the original results, will need to include infants at low risk of developing autism, allowing doctors to use the test on any infant—not just those with autistic siblings.
 </p>
<p>
  Other desired improvements include lowering the cost of diagnostic tests. Here’s Nicholette Zeliadt,
  <a href="https://www.scientificamerican.com/article/brain-scans-may-forecast-autism-in-babies/">
   reporting
  </a>
  for Scientific American:
 </p>
<blockquote>
<p>
   The type of brain scan the researchers used costs several thousand dollars, but more noninvasive and affordable methods, such as electroencephalography or near-infrared spectroscopy, might one day be used in clinics.
  </p>
</blockquote>
<p>
  For decades, scientists have been looking for early signs of neural or behavioral developments associated with autism. An earlier diagnosis would allow doctors to educate parents and begin behavioral therapy before symptoms manifest.
 </p>
</section>
<p>
 Photo credit: R.W. Emerson et al., Science Translational Medicine (2017)
</p>

Air pollution is an issue around the world, though its effects are not evenly distributed.

Too Much Pollution for One Place

<p>Emissions from waste treatment facilities and power plants contribute to a slow-motion public health disaster in Chester, PA.</p>

Earth’s Microbial Life May Have Been Able To Survive On Mars

<section class="entry-content instapaper_body clearfix" itemprop="articleBody">
<div class="add-container clearfix" id="add-block-placer">
</div>
<p>
  Over the past few years, the
  <i>
   Curiosity
  </i>
  rover has dug up clues suggesting that Mars’s Gale Crater once hosted a liquid-water lake.
 </p>
<p>
  Now, a new report says that the lake may have been long-lasting and chemically diverse—two qualities that suggest, if the lake were on Earth, that it would have supported a rich diversity of microbial life.
 </p>
<figure class="richtext-image full-width">
<img alt="Curiosity Self Portrait" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/curiosity-self-portrait-1.width-990_S7qUi4M.jpg"/>
<figcaption>
</figcaption>
</figure>
<p>
  In a paper published in
  <i>
   Science
  </i>
  last week, Joel Hurowitz of Stony Brook University describes an ancient lake that was chemically divided, with oxygen-poor water in deeper parts of the lake and oxygen-rich water closer to the surface. Different microbes thrive at different oxygen concentrations, meaning each layer of the lake would have been capable of supporting a different form of microbial life.
 </p>
<p>
  The analysis of the crater’s layers of sediment and chemical contents also suggest the planet would have been warm enough during the period spanning 3.1 to 3.8 billion years ago to support an aquatic lake more or less continuously. The rover has now traveled more than 100 meters vertically up the lake bed,  allowing the team to say with more certainty that the lake was sustained for a long period of time.
 </p>
<p>
  Since the scientists are studying rocks that are billions of years old on a planet a hundred million miles away, it can be difficult to detect the subtle signatures left by the lake. “I think [Hurowitz’s] seminal contribution is the chemistry,” said Raymond Arvidson, a scientist on the
  <i>
   Curiosity
  </i>
  mission who did not contribute to the new paper.
 </p>
<p>
  The precise data from the rover allowed the mission team to understand “the detailed and very nuanced changes in chemistry within the lake and changes in the environment over time,” said Ashwin Vasavada, a project scientist at NASA’s Jet Propulsion lab and a co-author of the paper. “I’m impressed with the level of detail that our [scientific equipment] was able to extract from these rocks,” he said.
 </p>
<p>
  The rover landed in Gale Crater in 2012 with the aim of determining whether the planet had ever been habitable to life found on Earth.
  <i>
   Curiosity
  </i>
  landed at the foot of  a five-kilometer tall mountain containing tens of millions of years of climate data locked in its layers of sediment—an ideal window into Mars’ climatic history. In 2014 and 2015, John Grotzinger of Caltech used data from
  <i>
   Curiosity
  </i>
  to argue that Gale Crater contained a liquid-water lake at some point between 3.1 and 3.8 billion years ago. He also characterized the physical makeup of the crater, determining, among other things, the ages of the layers. Hurowitz developed his theory by matching the chemical data to Grotzinger’s physical model.
 </p>
<p>
  These new findings suggest that Mars once supported a range of chemical environments that may have shared more in common with present-day Earth than scientists previously believed. “The more we look at Mars the more complicated it becomes and the more interesting it becomes,” Arvidson said. “And the more it looks like portions of the lake were habitable 3.18 to 3.8 billion years ago.”
 </p>
</section>
<p>
 Image credit: NASA
</p>

The Moon’s Interior Might Be Wet

<section class="entry-content instapaper_body clearfix" itemprop="articleBody">
<div class="add-container clearfix" id="add-block-placer">
</div>
<p>
  Much of the moon’s interior may contain water, new research finds.
 </p>
<p>
  Scientists from Brown University found evidence of water from satellite imaging of the remains of volcanic eruptions across the surface of the natural satellite. Since this material was expelled from below the moon’s surface, this suggests that the water came from the moon’s mantle. And nearly all the volcanic, or pyroclastic, deposits studied contained evidence of water, suggesting that the water is spread out across the planet’s whole interior and is relatively plentiful.
 </p>
<figure class="richtext-image full-width">
<img alt="" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/145983.width-990_kCIcYZa.png"/>
<figcaption>Evidence from ancient volcanic deposits suggests that lunar magma contained substantial amounts of water, bolstering the idea that the moon's interior is water-rich.
        
    </figcaption>
</figure>
<p>
  Here’s Space.com’s Samantha Mathewson talking to Ralph Milliken, the study’s lead author:
 </p>
<blockquote>
<p>
   “Our work shows that nearly all of the large pyroclastic deposits also contain water, so this seems to be a common characteristic of magmas that come from the deep lunar interior,” Milliken said. “That is, most of the mantle of the moon may be ‘wet.’ ”
  </p>
</blockquote>
<p>
  Scientists first began to suspect that the moon contained more than trace amounts of water back in 2011, when volcanic glass beads from the Apollo 15 and 17 missions were found to contain similar amounts of water to volcanic rock on Earth, suggesting that near the source of the Apollo samples, the moon’s interior contains as much water as Earth’s.
 </p>
<p>
  But the possibility remained that these samples were anomalous, and that the rest of the moon’s interior contained very little water. The fact that Milliken’s team, which published the research yesterday in
  <em>
   Nature Geosciences
  </em>
  , was able to find water in so many places suggests that the Apollo beads are representative of the entire mantle.
 </p>
<p>
  What’s impressive about this research is that it detects the presence of water without even landing on the moon. Satellite equipment measured the wavelengths of sunlight reflected by the moon in order to determine the minerals and compounds contained on the surface.
 </p>
<p>
  This finding raises the question of the water’s origin. Scientists previously believed that the collision that formed the moon produced too much heat for water to survive. So either the collision wasn’t too hot, or something else must have brought the moon its water.
 </p>
</section>
<p>
 Photo Credit: Olga Prilipko Huber
</p>

Should Testosterone Be Regulated in Female Athletes?

<div class="related"></div>
<p>
 In 2014, Indian sprinter Dutee Chand was barred from competing in the Commonwealth Games, an international sporting tournament between former territories of the British Empire. Chand hadn’t doped—a rampant problem in the sport—or consumed any illicit substances.
</p>
<p>
 But officials deemed that Chand, who was not favored to win the competition, had a seemingly unfair advantage: her body naturally produced a lot of testosterone.
</p>
<p>
 At least, that’s according to a regulation issued by the International Association of Athletics Federation (IAAF). Suspended in 2015 by the Court of Arbitration for Sport (CAS), the regulation was aimed at females whose bodies produce unusually high levels of androgens, a group of hormones that includes testosterone. Concerned in part that this condition, called hyperandrogenism, gave female athletes an unfair competitive advantage, the IAAF ruled that if athletes were unable to prove their body was incapable of using the testosterone, women with over 10 nanomoles of testosterone per liter of blood would either have to undergo surgery or take hormone suppressants before they would be allowed to return to competition.
</p>
<figure class="richtext-image full-width">
<img alt="Seb Coe" class="richtext-image full-width" src="https://www.pbs.org/wgbh/nova/media/images/seb-coe.width-990_IJFToj5.jpg"/>
<figcaption>IAAF president Sebastian Coe announced last summer that the governing body would appeal the CAS's suspension.
        
    </figcaption>
</figure>
<p>
 Men typically have much higher testosterone levels then women, and the IAAF believes that this is part of the reason why, on average, elite men outperform elite women by about 10% in track and field events. Take, for example, Genzebe Dibaba, an Ethiopian distance runner who holds five women’s world records between indoor and outdoor track and field. While Dibaba runs a blazing fast 4:13 mile, all twelve American high school boys at this year’s Brooks P.R. Invitational, the premiere high school meet of the summer, bettered Dibaba’s fastest career time. It would seem that we segregate men and women in track and field events with good reason—otherwise, one of the best female milers the world has seen in years would struggle to compete in national meets at the high school level.
</p>
<p>
 The IAAF argues that to uphold the integrity of women’s athletics, testosterone levels require greater scrutiny. The organization has until today to present evidence to the CAS that they hope will convince the court to reinstate the regulation.
</p>
<div class="pullquote">
<p>
 Most experts agree that the IAAF’s body of evidence is unlikely to convince the CAS to end the suspension.
</p>
</div>
<p>
 It’s expected that the IAAF will include in its package of evidence
 <a href="http://bjsm.bmj.com/content/early/2017/06/26/bjsports-2017-097792">
  a study published earlier this month
 </a>
 in the British Journal of Sports Medicine that links testosterone levels to athletic performance in a subset of women’s track and field events. While the authors conclude that their findings suggest that female athletes with high testosterone levels have a competitive advantage in these events and imply that they support the IAAF’s regulation, other scientists argue that the study is limited, lacks conclusive evidence, and that these conclusions about the research’s broader implications are unsubstantiated.
</p>
<div class="ad"></div>
<p>
 Most experts agree that the IAAF’s body of evidence is unlikely to convince the CAS to end the suspension. But the ban’s ethical complications are manifold—and that’s where opinions differ.
</p>
<p>
 Just about everyone agrees that the sport’s governing body should regulate athletes’ use of unnatural substances, like steroids. But to what degree should they control what occurs naturally in people’s bodies?
</p>
<h2>
 The History of Sex Testing
</h2>
<p>
 Sorting people into one of two of categories isn’t easy, because sex is not a neat binary of male and female, says Katrina Karkazis, an anthropologist, bioethicist, and senior researcher at Stanford University’s Center for Biomedical Ethics whose research focuses on intersex traits. Scientists used to think people could either have an X and a Y sex chromosome, and were therefore male, or two X chromosomes, and were therefore female. But as Karkazis explains in
 <a href="http://www.tandfonline.com/doi/full/10.1080/15265161.2012.680533?src=recsys">
  her 2012 paper
 </a>
 in The American Journal of Bioethics, those aren’t the only two options. Some people are born with two X chromosomes and one Y chromosome. Also, not everyone has the same sex chromosome pairing in every cell—some people have some cells with an XY pairing and other cells with an XX pairing.
</p>
<p>
 There are also at least five other markers of sex, including hormones, internal genitalia, and external genitalia, and the way that these markers—like chromosomes—express themselves is also not black and white. To further complicate things, a person might have one of these markers present as male, another present as female, and a third present as something in between—an intersex trait.
</p>
<p>
 Sports’ governing bodies struggled for decades with what to do with athletes who can’t be sorted into one of these two categories, resulting in numerous horror stories. Jaime Schultz, a professor of kinesiology at Penn State,
 <a href="https://theconversation.com/so-what-if-some-female-olympians-have-high-testosterone-62935">
  described in The Conversation
 </a>
 “nude parades” in the 1960s in which female athletes were forced to present themselves naked to gynecologists at the 1966 European Championships and the 1967 Commonwealth Games. Later, the IAAF switched their chromosome testing to a less invasive but still ethically questionable cheek swabbing.
</p>
<p>
 The IAAF and International Olympics Committee (IOC) ended systematic sex testing in the 1990s. But individual athletes have still been subject to scrutiny by the sport’s governing bodies, most recently Chand—the Indian sprinter—and South African 800-meter runner Caster Semenya. Because of her dominant performance at the 2009 World Championships and her stereotypically masculine build, Semenya, a teenager at the time, was “reportedly subjected to a two-hour examination during which doctors put her legs in stirrups and photographed her genitalia.” After the championships, “intensely intimate details about Semenya’s body became a topic for public debate and scrutiny,” Karkazis wrote in
 <a href="http://www.tandfonline.com/doi/full/10.1080/15265161.2012.680533?src=recsys">
  her 2012 paper
 </a>
 .
</p>
<p>
 After Chand appealed the 2014 ban, the CAS reinstated her and suspended the hyperandrogenism regulation. The CAS wrote in its decision that “the Hyperandrogenism Regulations are based on an implicit assumption that hyperandrogenic females enjoy a
 <i>
  significant performance advantage
 </i>
 over their non-hyperandrogenic peers, which outranks the influence of any other single genetic or biological factor.” It gave the IAAF two years to gather evidence supporting this assumption.
</p>
<h2>
</h2>
<div class="newsletter"></div>
<h2>
 The IAAF Evidence
</h2>
<p>
 Joanna Harper, a medical physicist and the only transgender person ever to be an advisor to the IOC on matters of gender and sport, says that the IAAF is likely to include
 <a href="http://bjsm.bmj.com/content/early/2017/06/26/bjsports-2017-097792">
  a study by Stéphane Bermon
 </a>
 , a physician and exercise physiologist, that’s receiving a lot of public attention.
</p>
<p>
 The study divided athletes in each track and field event at the 2011 and 2013 World Championships into three groups based on their fT levels (fT stands functional testosterone, or testosterone that the body can use). The authors then tested for a statistically significant difference between the average times of athletes in the upper third of fT levels and those in the lower third. It concluded that “female athletes with high fT levels have a significant competitive advantage over those with low fT” in five track and field events, and that this advantage should be considered by those writing legislation.
</p>
<p>
 While it’s published in the peer-reviewed and highly respected BJSM, the study has raised a few eyebrows. Schultz is skeptical of the research’s merit because of the authors’ ties to the IAAF. Bermon, the lead author, is a member of the IAAF’s Medical and Antidoping Commission, and co-author Pierre-Yves Garnier is the Director of the IAAF’s Health and Science Department. Schultz says that “the federation has been clear that it intends to return to court with proof that testosterone is linked to improved athletic performance,” so the IAAF has a vested interest in producing results that favor the regulation. “It’s very clear that the article is written with a purpose of…[defending] that particular regulation,” Karkazis echoes. “They have a dog in this fight.” Neither author was available for comment.
</p>
<p>
 Beyond the conflict of interest, Garnier’s reputation has recently taken a hit—according to
 <a href="http://www.reuters.com/article/us-sport-doping-athletics-suspensions-idUSKCN0YW0VA">
  Reuters
 </a>
 , the IAAF suspended Garnier last summer for allegedly receiving cash payments in a cover-up of Russian doping cases.
</p>
<p>
 Three statisticians who did not contribute to the research—Dorit Hammerling of the National Center for Atmospheric Research, Joe Guinness of North Carolina State University, and Richard Smith of the University of North Carolina—say that the paper does have some statistical merits. They wrote in a group email with NOVA Next that the paper successfully demonstrates a measurable difference in performance between female athletes with high testosterone and those with low testosterone in the five relevant events.
</p>
<p>
 But these findings do come with a few caveats. First, the authors ran tests on 43 events (21 women’s and 22 men’s events), so it’s possible that a few of the five statistically significant results are due to random error. Second, the authors didn’t account for the fact that almost a fifth of the female athletes competed in both World Championships, so a significant number of subjects are counted twice. The authors also only had access to one time and one fT level for each athlete, so they could only analyze a narrow sliver of each athlete’s career. Smith thought a different type of analysis would have been better given the limited amount of available data, but he said “that would require a much higher level of statistical expertise than is show in the rest of the paper.” Smith said he would have liked to see the analysis performed excluding known dopers, whose artificially boosted T levels could have skewed the results.
</p>
<div class="pullquote">
<p>
 Two runners can have different times without one having a significant competitive advantage over the other.
</p>
</div>
<p>
 While the authors are justified in arguing that they found five significant results, some of their other claims are harder to defend. Smith points out that there’s a difference between a statistically significant result and a practically significant result. Two runners can have different times without one having a significant competitive advantage over the other. And while most in the track and field community would consider the two-second difference found between low-T 800 meter runners and high-T 800 meter runners to be significant, that’s only the authors’ best guess for the time difference—it could be a difference as small as a fraction of a second, or as large as four or five seconds. As Smith says, “the broader implications are unclear.”
</p>
<p>
 This distinction is pivotal for the IAAF. Karkazis says “the CAS didn’t say you needed a statistically significant finding, but a finding of a performance difference of a particular magnitude,” a magnitude that the study did not find. The three statisticians agree that the paper doesn’t “[settle] the issues regarding athletes such as Chand or Semenya whose eligibility to participate in female events has been challenged.”
</p>
<p>
 Finally, while the authors make clear in one part of the paper that what they’ve found is merely a correlation and that they can’t conclude that the higher fT levels are causing the better performances, their implication that this evidence is in support of the regulation makes it sound like they actually have found causation. Karkazis says that these are conclusions that “support the regulation but which the science itself in the study doesn’t support.”
</p>
<h2>
 Testosterone and ‘Fair Sport’
</h2>
<p>
 Harper acknowledges the limitations of the study but argues that “you’d see even a more robust difference between the low T and the high T athletes” if the authors had more data to work with. Much of the performance difference between men and women can be prescribed to testosterone differences, she says.
</p>
<p>
 But Karkazis begs to differ. “There are plenty of studies that show a much more complicated and equivocal relationship than what policy makers would like to claim,” she says.
</p>
<p>
 Schultz agrees, saying that “so many different variables—internal and external—have to align for top performance.” But Harper argues that it’s misleading “to compare testosterone advantages to other natural advantages,” saying the advantages of testosterone far outstrip those of other biological components. She references as evidence studies conducted in Germany in the 1970s and 1980s showing that increases in exogenous testosterone were “spectacularly effective” at improving performances in elite female athletes.
</p>
<p>
 The IAAF claims that the hyperandrogenism regulation protects the integrity of female athletics and promotes “fair sport.” But Karkazis says that by focusing on testosterone, a singular biological component, the IAAF overlooks not just other biological factors, but also inevitable social and economic inequalities in athletics. Athletes in richer countries, for example, have access to better training facilities, coaches, and equipment, and can afford to dedicate more time to training. Professional athletics will always be littered with people who have incredible genetic gifts and socioeconomic benefits. The existence of professional sports itself may even depend on that un-level playing field.
</p>
<p>
 Regardless of where experts align themselves in the debate over testosterone, most seem to agree that the IAAF’s package of evidence will not be enough to convince the CAS to reinstate the hyperandrogenism regulation. Ross Tucker, an exercise physiologist and strong advocate for the regulation,
 <a href="http://sportsscientists.com/2017/07/testosterone-performance-intersex-athletes-will-iaaf-evidence-enough/">
  wrote on his blog
 </a>
 “The Science of Sport” following the publication of the new Bermon study that “the IAAF evidence does not go far enough, either in terms of the depth or the range.”
</p>
<p>
 “To reduce an athlete’s excellence to her androgen serum level or to disqualify an athlete because of her biology doesn’t strike me as appropriate,” says Schultz. Karkazis, too, argues that women shouldn’t be forced to undergo medical treatment just so they can continue to compete. “The athletes that we’re talking about are no different than any of the other women who are born and lived as women for their entire lives. And I just cannot for the life of me see a reason to treat those women differently.”
</p>
<p>
 Photo credits:
 <a href="https://www.flickr.com/photos/globalsportsforum/6966828681/in/photolist-bBCPrT-dQmgwk-bBCVNk-boHY7C-dQmgnv-bBCWyK-aHtegt-77diQp-7d4vEM-bBCRb6-bW5n7m-a7FejC-5sTZG1-9GYjxc-e3vKUF-fczEka-boHVVs-fjVj1o-bxhuVb-e3vKXF-fczEv2-ceHp2L-fczEH2-ceHppG-9qBfdC-fjVQLf-auP7pc-fjVNtN-ou6bX9-auRMpN-aEB99p-bXkZ6x-ceHpfS-bXkZ3B-fcPYzd-ceHp6A-bW5n9f-bXkZeM-9qBfdG-5XeG8q-34Qdyx-eBZDvU-boHZzm-bXkZbT-B3r2A5-dZMJ7R-8LocBS-7mBYMi-fczE4r-cHFPow">
  Global Sports Forum/Flickr (CC BY-NC 2.0)
 </a>
 ,
 <a href="https://www.flickr.com/photos/az1172/6141323034/in/photolist-78NgQv-8uTc4N-cQ3AWw-d9bmpU-amFTnU-cRCJDY-6YGtw4-LhUfcY-cSFkUN">
  André Zehetbauer/Flickr (CC BY-NC 2.0)
 </a>
</p>

<p>Scientists debate the ethics of regulating female athletes’ testosterone levels.</p>

Will Sullivan

Articles