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Nettie Stevens Day

July 7, 2025/0 Comments/in July

Nettie Stevens

Nettie Stevens Day celebrates the scientist who discovered XX and XY chromosomes determine sex. But few know of her contributions because the credit went to a man — who got it wrong.

Nettie Stevens studied mealworms and found that a male’s sperm carried both X and Y chromosomes, while a female’s eggs contained only X chromosomes. She concluded that sex determination must come from fertilization of the egg by the sperm. In 1905, she submitted a paper for publication, reporting her results.

Meanwhile, Columbia University scientist Edmund Beecher Wilson had reached the same conclusion, sort of. He was asked to review Stevens’ paper prior to its publication; his own paper had reportedly already gone to press, negating any possibility of dishonesty.

Historian Stephen Brush disputes the timeline in The History of Science Society: “It is generally stated that E. B. Wilson obtained the same results as Stevens, at the same time,” he writes. But “Wilson probably did not arrive at his conclusion on sex determination until after he had seen Stevens’ results.”

In fact, Wilson wrongly asserted that environmental factors could influence sex. Stevens insisted it was all due to chromosomes. At the time, there was no way to prove either theory. However, it has been known for decades that Stevens got it right. That should render the question of who published first irrelevant.

In spite of that, Wilson and Stevens were credited with making the fully correct discovery independently. Wilson received the lion’s share of accolades while Stevens was often mistakenly referred to as a “lab technician.” Brush states, “Because of Wilson’s more substantial contributions in other areas, he tends to be given most of the credit for this discovery.”

The fact that Nettie Stevens had two X chromosomes certainly contributed to the lack of recognition. Her own accomplishments refute Brush’s assertion. She published 40 papers and was about to attain full research status at Bryn Mawr when she died of breast cancer on May 4, 1912, at the age of 50.

She — and Wilson, too — have been all but forgotten since then. In 1933, fellow scientist Thomas H. Morgan received the Nobel Prize for his pioneering work in chromosomal research, even though he didn’t espouse the theory until years after Stevens and Wilson had published their papers.

Stevens once remarked to her students that their questions were always welcome “so long as I keep my enthusiasm for biology; and that, I hope, will be as long as I live.”

Let’s remember Nettie Stevens today. And tomorrow and the next day….

May 26 is Sally Ride Day

May 26, 2025/0 Comments/in May

Ride monitors control panels from pilot’s chair on the flight deck.

Today is Sally Ride Day. It celebrates the achievements of the astronaut, astrophysicist, engineer, philanthropist and author best known as the first American woman to travel to space. Today’s date honors her birthday on May 26, 1951.

Women weren’t considered for America’s space program until 1978. Ride was selected from the first group to apply after NASA announced it had changed its policy. Her training included learning to parachute jump, fly a jet plane, survive a water landing and handle extreme G-forces and weightlessness.

She was picked as a member of the space shuttle Challenger’s STS-7 crew, scheduled for liftoff on June 18, 1983. Commander Robert Crippen chose her in part because the mission required the use of a robotic arm that Ride had helped to develop.

At pre-flight news conferences, she was asked if spaceflight would affect her reproductive organs, if she planned to have children, how she would handle menstruation in space, if she would wear a bra, and apply makeup. Asked if she cried on the job when under stress, Ride laughed and said, “Why don’t people ask (pilot) Rick (Hauck) these questions?”

Diane Sawyer of CBS News asked Ride to demonstrate how she would utilize the shuttle toilet’s new privacy curtain. On The Tonight Show, Johnny Carson joked that the flight would be delayed while she found a purse to match her shoes. At one NASA news conference, Ride said, “It’s too bad this is such a big deal. It’s too bad our society isn’t further along.”

On launch day, she focused on the task ahead. In an interview on the 25th anniversary of the flight, Ride recalled, “I didn’t really think about it that much at the time, but I came to appreciate what an honor it was to be selected to be the first (American woman) to go into space.”

After its successful mission to deploy two communications satellites, Challenger landed at Edwards Air Force Base, CA, on June 24, 1983. At the time, Ride told reporters, “The thing that I’ll remember most about the flight is that it was fun. In fact, I’m sure it was the most fun I’ll ever have in my life.”

She returned to space on October 5, 1984. (Kathy Sullivan, a fellow member of the STS-41G crew, became the first American woman to walk in space.) Ride’s third flight was canceled after the Challenger exploded shortly after takeoff on January 28, 1986. She served on the Presidential Commission that investigated the accident and returned in 2003 after the loss of the STS-107 crew to serve on NASA’s Columbia Accident Investigation Board.

Ride left NASA in 1987 to become a science fellow at the Center for International Security and Arms Control at Stanford University. Two years later, she became a physics professor and director of the University of California’s California Space Institute.

In 2001, she founded Sally Ride Science, which provides programs, materials, and teacher training to schools in order to motivate students, especially girls and minorities, to study STEM (science, technology, engineering, and math). She wrote six science books for children. Intensely private about her personal life, she requested that NASA keep her health issues out of the press. She died of pancreatic cancer on July 23, 2012, at the age of 61.

“As the first American woman to travel into space, Sally was a national hero and a powerful role model,” President Barack Obama said in a statement released shortly after her death. “She inspired generations of young girls to reach for the stars and later fought tirelessly to help them get there by advocating for a greater focus on science and math in our schools.”

Ride was posthumously awarded the Presidential Medal of Freedom, the highest civilian award in the U.S., which was presented to her life partner Tam O’Shaughnessy at a ceremony at the White House on November 20, 2013.

“Sally’s life showed us that there are no limits to what we can achieve,” said Obama, “and I have no doubt that her legacy will endure for years to come.”

Sources:
American Woman Who Shattered Space Ceiling, New York Times
Sally Ride Remembered as an Inspiration to Others, NASA

May 2 is Tuatara Day

May 3, 2025/0 Comments/in Holidays by Month, May

Today is Tuatara Day. On May 2, 1867, scientists first recognized that the tuatara, a reptile found only in New Zealand, is not a lizard (Squamata) as originally thought. Why is this important? Like Tigger and the Highlander, there can be only one. The tuatara is the sole surviving representative of its own group (Rhynchocephalia), which existed alongside dinosaurs.

Photo credit: Alison Cree

Although Rhynchocephalia is the closest living relative of Squamata, which includes both lizards and snakes, the two groups diverged about 250 million years ago. To put that family relationship into perspective, a human is more closely related to, say, a kangaroo than the tuatara is to a lizard.

Illustration: Marc E H Jones

Tuatara is a Māori name meaning “peaks on the back,” a reference to its spiny crest, and the species has been identified by the Māori people as a taonga (treasure). It is nocturnally active and spends its days basking in the sun or in a burrow. Although capable of digging the burrow itself, it prefers to use those made by birds.

Unlike a lizard, it has two rows of teeth on the top, which are fused to the jawbone. When feeding, the bottom row bites between the upper rows of teeth, then slides forward in a shearing motion that allows it to decapitate its prey, as evidenced by reports of birds’ headless bodies found outside their lairs. Not a nice way to treat one’s landlord, certainly.

Tuatara reach sexual maturity around age 14 and have been known to live up to 70 years in the wild and much longer in captivity. The male’s lack of external genitalia makes it useful to research the evolution of the phallus in amniotes (mammals, birds, and reptiles). Because females only breed every two to five years, producing six to ten eggs that require incubation for up to a year, population numbers are low and protected, making it nearly impossible to obtain embryos for study.

In 2015, researchers used 3-D technology to virtually reconstruct an embryo from slides that had been prepared in 1909 and left in a collection at Harvard University ever since. Their finding that the embryo possessed genital buds suggests a single evolutionary origin of amniote external genitalia. As researcher Thomas J. Sanger wrote, “Without access to these museum specimens we would have no way of knowing the secrets of the tuatara penis.”

Author’s note: As a layperson, while I found this subject fascinating, I began to feel I was, at the very least, invading the tuatara’s privacy and, at worst, straying into reptile porn territory. I’m pretty sure my Google search history has been flagged.

Once plentiful, tuatara numbers have decreased since the arrival of humans, dogs, and Pacific rats about 800 years ago. In particular, rats have decimated the number of tuatara, most likely due to competition for food and/or predation on eggs and juveniles. Rats, as well as possums and stoats, are being exterminated as part of a government initiative called Predator Free 2050 to save the tuatara and other native species from extinction. The cat, another introduced species, has apparently been exempted from the culling thus far. PETA remains strangely silent on New Zealand’s rodenticide.

Climate change is another threat to the tuatara, who exhibit temperature-dependent sex determination. The warmer an egg’s environment, the more likely the hatchling will be male. Conservationists are taking steps as temperatures rise, such as carefully relocating tuatara to milder areas to keep the ratio from skewing so male that the population collapses.

Although Tuatara Day was first celebrated in 2017 on the 150th anniversary of the scientists’ recognition, boasting its own hashtag, #150NotALizard, on social media, one tuatara had been making headlines since 2009. That’s when Henry, a tuatara living at New Zealand’s Southland Museum, achieved celebrity status after becoming a first-time parent at the ripe old age of 111.

His mate Mildred, a tuatara in her seventies, had apparently forgiven Henry for their disastrous first date 25 years earlier when he’d bitten off her tail (twice!) and seemed unconcerned by their age difference. (We don’t like to use the phrase “robbing the cradle” since tuatara sometimes eat their young. It’s a bit of a sore subject.) Mildred laid 12 eggs, and on January 25, 2009, after 223 days of incubation, 11 baby tuatara hatched.

Photo credit: Tim Rooke (Shutterstock)

Seven years later, Henry met Prince Harry on the then-royal’s tour of New Zealand. (Fun fact: Harry was christened Henry at birth as well.) There’s no mention of whether Mildred and the kids were in attendance as well. Since then, another female named Lucy has been added to the mix. They’ve had so many babies that the randy throuple had to be separated while staff worked to find homes in the wild for some of their offspring. This year, Henry will celebrate the 55th anniversary of his arrival at Southland Museum. The museum now has more than 100 tuatara in residence at different stages of development.

No word on how Henry felt about Megxit.

Happy Tuatara Day!

Sources:
Tuatara – Current Biology, Volume 22, Issue 23
Rare reptile holds clue to penis evolution – Science News
Evolution: One Penis After All – Current Biology, Volume 26, Issue 1
Not a lizard nor a dinosaur, tuatara is the sole survivor of a once-widespread reptile group – The Conversation
Reproduction of a Rare New Zealand Reptile, the Tuatara Sphenodon punctatus, on Rat‐Free and Rat‐Inhabited Islands – The Society for Conservation Biology
Resurrecting embryos of the tuatara, Sphenodon punctatus, to resolve vertebrate phallus evolution – Royal Society
Predator Free 2050 – New Zealand Department of Conservation
Predator Free 2050: New Zealand ramps up plan to purge all pests – BBC News
When a species can’t stand the heat – Science News Explores
Henry the tuatara is a dad at 111 – The Independent
Prince Harry meets reptilian namesake in New Zealand – BBC News
He’s 130, with three eyes and two girlfriends: meet New Zealand’s beloved tuatara Henry – The Guardian
Prince Harry strokes 118 year-old reptile – The Telegraph via YouTube
Tuatara – Southland Museum NZ – temporarily closed

October 23 is National Mole Day

October 23, 2017/0 Comments/in October

National Mole Day is not a time to pay tribute to cute furry diggers, secret agents, Mexican sauces, freckles or skin tags. (By the way, you really ought to have that thing checked out.)

Once a year on October 23 from 6:02 a.m. to 6:02 p.m., National Mole Day celebrates Avogadro’s Number (6.02 x 1023), a unit of measurement in chemistry. Mole Day originated in an article from The Science Teacher in the early 1980s. Inspired by the article, a chemistry teacher in Wisconsin created the National Mole Day Foundation on May 15, 1991.

In 1811, Lorenzo Romano Amedeo Carlo Avogadro di Quaregna e di Cerreto—Amadeo Carlo Avogadro to his parents—proposed a law stating that equal volume of all gasses, at the same temperature and pressure, have the same number of molecules.

Avogadro contradicted better-known scientists of his time, didn’t publish his work in highly regarded journals and hailed from Italy, which had fallen out of favor as a site of scientific innovation. It took almost a hundred years for the scientific community to catch on. Chemist and Nobel laureate Jean Baptiste Perrin proposed in 1909 that the total number of particles contained in one mole be called the Avogadro Constant.

6.02×10^23

One mole is a mass (in grams) whose number is equal to the molar mass of the molecule. Because atoms are so small, they can only be measured in enormous numbers, on the scale of Avogadro’s number.

1 Mole = ∼ 602,200,000,000,000,000,000,000

It ‘s hard to imagine such a large number. Oklahoma State University has some useful analogies to help envision it:

Astronomers estimate that there is a mole (6.02 x 10²³) of stars in the universe.
Water flows over Niagara Falls at about 650,000 kL (172,500,000 gallons) per minute. It would take 134,000 years for one mole of water drops to flow over Niagara Falls.
One mole of marbles, each 2 cm in diameter, would form a mountain 116 times higher than Mount Everest. The base of the marble mountain would be slightly larger than the area of the USA.

National Mole Day has always been about fostering interest in chemistry. It has been celebrated by teachers, students and schools for decades and inspires participants to create activities, thought experiments and even music videos to make learning about Avogadro’s Number fun.

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6.02×10^23

1 Mole = ∼ 602,200,000,000,000,000,000,000

Avogadro would be so proud!