The number and quality of sperm in men's semen are down, giving rise to various movements to avoid 'spermpocalypse.'

Male infertility, due to declining sperm counts or quality, accounts for about half of the cases of infertility among couples. Recent research has found that global sperm counts fell, on average, by 1.2% per year between 1973 and 2018—from 104 million to 49 million per milliliter. From 2000, this rate of decline accelerated to more than 2.6% per year.

We've evolved to make pregnancy a complex and difficult process. From the initial development of the blastocyst, to the energy and nutrients needed to grow a new human, our bodies are both fighting and supporting fetal development.

Known as the Star system—for Sperm Track and Recovery—it uses artificial intelligence to help identify and locate "hidden" sperm in men with a rare infertility condition called azoospermia. The condition affects about 1% of men, and these individuals have sperm counts low enough that the individual spermatozoa in their ejaculate may be undetectable. In late 2025, the first baby was born after the child's parents used this assistive technique to locate sperm.

In this series of comic-style panels, a "fellowship" of sperm cells travels through fictionalized versions of reproductive anatomy on their way to an egg cell. Each panel includes informative commentary on each step of the adventure, with research insights provided by a reproductive biologist, a biomedical scientist, and an andrologist.

Throughout human history, scholars and researchers have speculated on the origin of human reproduction. It wasn't until the late-19th century that the physical process of egg fertilization via sperm cells was observed (in sea urchins), forming the basis for modern fertility research.

From refined artificial insemination and microsurgical sperm extraction to experimental uterine transplants, scientific innovation is rapidly advancing potential fertilization technologies. But they come along with costly trials, some ethical dilemmas, regulatory issues, and more.

Girls are born with an estimated 1 million to 2 million eggs in their bodies, but around 10,000 die monthly before girls hit puberty. Scientists have not yet figured out why there's such an excessive number of eggs prior to menstruation, but they've calculated that there are roughly 300,000 to 400,000 eggs left at puberty.

Pretty much every species breaks down with an equal sex-ratio, with roughly the same number of males as females. But on the surface, it appears that most species wouldn't need many males to keep the population growing, with their energy-efficient, abundant sex cell production. So why is it equal? Scientists argue an equal ratio is the most evolutionarily stable. Learn about this quirk of biology here.

This article breaks down the global crash in fertility rates. According to researchers, a global crash in children being born will have a “jaw-dropping” impact on societies. Women are choosing to have fewer children as a result of more women in...

Pregnancies involving three kids or more have dropped 62% from 1998 to 2023, a trend that the Centers for Disease Control and Prevention links to fewer embryo transfers during assisted reproduction procedures—a transition prompted by more refined techniques and technical advances. Though multiple births can occur naturally, often pregnancies involving multiple births have been the result of efforts to ensure pregnancy success by transferring multiple embryos.

If current birthing trends persist, every hundred South Koreans today will have only six great-grandchildren between them. This crisis is a result of high expenses, harsh work-family trade-offs for women, declining marriage rates, and other societal factors. Some newer policies are helping to build incentives for having children, but larger issues also need to be addressed.

The US is dropping billions of sterile flies to stop a deadly parasite. Screwworm maggots eat animals alive, so scientists are collapsing the population by ensuring females can’t reproduce.

Researchers theorize that environmental factors, including shifts to less healthy diets, air pollution, infections, stress, climate change, and exposures to xenobiotics—substances like pesticides, plastics, and toxins that incite immune responses—may all be fueling epigenetic changes to our bodies that make people's immune responses go awry.

Much ado is made about falling marriage and birth rates worldwide, and how they might affect tax bases, retirement funds, and social standing. But this isn’t the first time marriage, and subsequently reproduction, have fallen out of favor. Some countries have resorted to drastic measures to restore the tarnished state of these hallowed institutions.

89% of the world’s population now live in countries with falling rates. Increasing costs of living, the financial burden of starting a family, and the rise of secularism are some of the key factors reducing marriage rates among the less affluent.

An estimated 25 million women pass through menopause annually, with a projected increase in the number of women in menopause in both lower-resource and higher-income populations in the years ahead, highlighting the social and economic value of focusing on menopause care.

A look at the companies offering surrogacy to the ultrarich—including Chinese men taking their reproductive cues from Elon Musk.

A study tracking 25,000 copies over 18 years revealed marriages tend to end in divorce more often when the woman is sick. Conversely, men's health issues do not impact divorce rates. Researchers noted that increased depression, potentially as a result of financial dependence, contributes to the disparity. Generally, most marriages do not end when a spouse becomes sick.

Across human trials, seed oils have not been shown to increase rates of disease or inflammation, with a study of over 800 Swedish men finding that higher seed oil diets were linked to living longer. Reviews of these trials found better health outcomes when saturated fats were replaced with seed oils.

Research suggests that one in every five butterflies is lost due to pesticide use, habitat loss, and climate change. Playing a vital role in pollination, their declining populations threaten plant reproduction and the health of ecosystems.

Few animals are known to experience menopause, raising questions about why it would be evolutionarily advantageous to have women survive past their reproductive years. One leading hypothesis is the grandmother hypothesis—older women and other species known to experience menopause, like whales, can aid families and pass down knowledge to future generations.

Nearly all studies researching the biology of aging don't consider menopause in their setup. In part, that's because menopause is difficult to emulate in animal models. Menopause is uncommon in the animal world beyond humans and whales. This presents a problem for medicine and science because about 75% of aging-related diseases are likely influenced by menopause.

One in 44 men in the US will die from prostate cancer, while one in eight will be diagnosed with it. Commonly viewed as the safest cancer to have, screenings can save lives—but they can also cause complications for otherwise benign cases of the disease.

Reproduction is a basic human function, and while we've spent decades in space, no research has been done into the process. With many discussing the possibility of human-occupied bases on the moon, Mars, and more, understanding how sex works outside...

The creation of a single cell produces 120,000 genetic mutations that can lead to cancer. This video investigates how our bodies proofread and autocorrect those mistakes.

Antimicrobial resistance is a global health threat, driven by the misuse and overuse of antimicrobials in humans, animals, and more. Estimates suggest superbugs could lead to $1T in healthcare costs by 2050, and the world faces a shortage of new drug development to meet the challenge.

Although no demographic data exist for more than 99% of the time humans have existed, this value can be estimated by tracking approximate population sizes over different periods and the birth rates within those periods. In 2022, about 6.8% of humans that have ever been born were alive.

Recent research has explored potential links between increased childhood cancer occurrence, particularly leukemia, and assisted reproductive technology (ART). Though some studies have detected this type of association, researchers caution that it remains unclear if ART itself, fertility drugs, underlying infertility of the parents, or other unknown factors may explain any increased cancer numbers among ART-conceived children. Overall, the incidence of cancer in children, regardless of conception method, is very low.

March Madness isn’t just a major sporting event—it’s also peak season for vasectomies. Urologists report a 50% increase during the tournament, as patients use recovery time as an excuse to watch nonstop basketball. Meanwhile, workplace distractions from bracket pools and game streaming are estimated to cost US businesses $17 billion.

As cells get larger, their volume grows much faster than the surface area through which nutrients and waste products pass, creating a bottleneck that eventually causes cells to die. This forces nearly all organisms visible to the naked eye to comprise enormous numbers of smaller cells, such as the approximately 30 trillion found in the average adult human.

Using stem cells from skin and mouth cells could save hopeful parents time and money and spare egg donors from significant amounts of discomfort throughout the process. There are potential consequences, not just for infertility treatment, but for the ability to create customized cells of any type.

Researchers at the Harvard T.H. Chan School of Public Health found that declines in pollinator populations would lead to higher rates of nutritional deficiencies, particularly in developing nations. Nations with large populations, such as China and India, would also be significantly impacted.

The increased use of antibiotics combined with an aging population, is projected to result in an almost 50% increase in global deaths from antimicrobial resistance each year. At the same time, antibiotic use for livestock is expected to increase by 30% over the same time frame.

Scientists have linked microplastics to immune system damage, hormone disruption, inflammatory diseases, and even cancer—yet most of their health impacts remain unknown due to limited research. Studies suggest we ingest about a credit card's worth of plastic weekly.

Marriage has taken drastically different forms than in the past. The transformation of marriage from a form of economic dependency for women to an equal partnership has forged demographic shifts. Richard Reeves, author of "Of Boys and Men," explains how economic and educational factors have potentially destabilized partnerships and changed patterns of “marriageability” for middle- and lower-class men.

Since 1990, antibiotic resistance has claimed at least one million lives annually and is projected to account for 39 million deaths between now and 2050 if current trends continue. The expanded use of antibiotics, particularly in agriculture, combined with a slowing pipeline of new drugs has led to the crisis.