A 194-year-old tortoise, and why a vaccine floors some people

Jonathan, an Aldabra giant tortoise living on the island of Saint Helena, is estimated to be about 194 years old, which makes him the oldest known land animal. A new study in Science Advances has now read his genome and his DNA methylation.

Methylation is a set of chemical tags on DNA that helps switch genes on and off. With age, those tags tend to drift into disorder, which researchers measure as methylation entropy. Across Jonathan and four other tortoises, entropy rose with age. But 272 gene switches, called promoters, stayed orderly in Jonathan and the two youngest animals while losing that order in the two older adults. Those promoters were enriched for genes tied to processing RNA and to mitochondria, the parts of the cell that make energy.

Jonathan also carried variants found only in him in 287 genes, and 12 of the potentially significant ones appear in aging databases.

The limits are built into the subject. This is one animal compared with four, two of them of unknown age. Nobody was allowed to draw Jonathan's blood, so the team worked from cheek scrapes and saliva and couldn't run RNA tests to see whether his unusual variants change gene activity. Only about 10% of promoters could be evaluated. The authors call their aging model a hypothesis and say the data cannot establish cause. Whether orderly energy genes matter for human aging is still an open question.

About 30% of five-year-olds report some bodily pain. Among people 100 and older, it's about 70%.

Those figures come from a Nature Medicine study that pooled self-reported pain from 6,125,459 people in 118 countries and territories, drawn from 902 population surveys collected between 1990 and 2025. The aim was a set of reference curves, something like a children's growth chart, showing how common pain is at each age.

Back pain topped the list at around 40%, and facial pain was rarest, at about 2%. Women reported more pain at all 11 body sites, and the gap widened for severe pain: their risk of high-intensity pain was about 1.5 times men's.

Place mattered as much as sex. At 80 and older, any bodily pain was 30.6 percentage points more common in the least developed settings than in the most developed. Smoking, obesity, and low income together accounted for an estimated 18.3% of the global pain burden, from 12.6% in sub-Saharan Africa to 27.1% in eastern Europe. Those estimates rest on associations, so they don't show that removing those factors would remove the pain.

The curves also don't follow anyone through life. Most of the data compare different people at different ages, gathered by surveys that worded questions differently and asked about different stretches of time. Some regions and age groups were thinly covered.

Under permanent daylight saving time, the latest winter sunrise in Toronto would come at 8:51 a.m. In Calgary it would be 9:40 a.m. Under standard time, both arrive an hour earlier.

That hour is the heart of an analysis in the Canadian Medical Association Journal, led by Raymond Lam. If Canada ends the twice-yearly clock change, the authors argue, it should keep standard time. Morning light helps set the body clock, which shapes sleep and mood. They cite estimates that seasonal affective disorder affects 1–3% of Canadians, and that up to 15% have milder seasonal shifts in mood and sleep.

The opposite choice is gaining ground. Yukon adopted permanent daylight saving time in 2020, British Columbia followed in March 2026, and in July the US House passed a bill to make daylight saving time permanent.

This is a policy argument, not a new study measuring how people sleep under each system, and the details here come from reporting on the paper. The authors acknowledge what their choice costs: standard time brings earlier winter sunsets.

Urolithin A is a compound made by gut bacteria and sold as a supplement for aging and blood-vessel health. A trial in JAMA Network Open put one of those claims to a controlled test.

At the University of Oklahoma, adults aged 40 to 64 with obesity took either 1,000 mg of urolithin A or a placebo every day for four weeks, with neither participants nor researchers knowing who got which. The main measure was how much the main artery in the arm widens, a test of blood-vessel function. The two groups did not differ meaningfully.

One secondary measure did shift. During a memory task, the urolithin A group showed larger blood-flow responses in a region at the front of the brain's left side. People did no better on the task itself, and a secondary result like this needs confirming before it means much.

The supplement was well tolerated, and more than 95% of doses were taken as planned. Still, the analysis covered 50 people, 74% of them women, at a single site for a month. It shows no health benefit, and whether that brain blood-flow signal leads anywhere would take a longer, larger trial to answer.

Two people get the same COVID-19 shot. One feels fine; the other spends the night with a fever. Fever is a common side effect, and it can make people wary of the next dose. A study in Science suggests part of the difference may lie in the bacteria living in our guts.

The researchers started with people. They collected stool from more than 170 people before and after a second or third dose, then compared those who ran worse fevers with those who had little or none. The high-fever group had more flagellin in their gut. Flagellin is the protein in the whip-like tails bacteria use to swim, so more of it suggests more mobile bacteria. That group also tended to show more gut inflammation.

A difference in stool samples could have many explanations, so the team moved to the lab. They exposed organoids, tiny lab-grown pieces of human intestine, to microbes from high-fever donors. Those microbiomes triggered stronger inflammation, and the response depended on flagellin.

Then came mice. Mice given fever-associated bacteria had a stronger temperature response, but only if they could sense flagellin. That points to flagellin doing something rather than just tagging along. There's a wrinkle: mice respond with a drop in temperature instead of a fever, so the mouse step parallels the human reaction rather than reproducing it.

The chain still has gaps. The human evidence is an association in about 170 people. Nobody yet knows why flagellin levels differ from person to person. Self-reported vegetarians tended to have lower levels, but diet wasn't tested as a way to change them. What the work offers is a testable explanation for a familiar puzzle: the same shot, landing in different guts.