Hello Nature readers,
Today we enjoy the month's best science images, hear from scholars about protests in Iran and learn how understanding canine diseases will save human lives.

The month's best science images

The world's oldest two-headed tortoise — named Janus, after the two-faced Roman god — celebrated his 25th birthday on 3 September. The Greek tortoise (Testudo graeca) was born at the Geneva Natural History Museum in Switzerland and has lived there ever since. He has two hearts, two sets of lungs and, according to museum staff members, two separate personalities. "The right head is more curious, more awake, it has a much stronger personality," says handler Angelica Bourgoin. "The left head is more passive and loves to eat."

See more of the month's sharpest science shots, selected by Nature's photo team.

DeepMind AI masters matrix maths

An artificial intelligence (AI) developed by the Google company DeepMind has tackled matrix multiplication. The AlphaTensor system leverages the skills that DeepMind's game-playing AIs use to beat human players at games such as Go and chess. Matrix multiplication is a widely used technique that involves multiplying numbers arranged in grids — or matrices — that might represent sets of pixels in images, air conditions in a weather model or the internal workings of an artificial neural network. AlphaTensor broke ground by finding shortcuts to solve problems with fewer steps.

Why is monkeypox losing chunks of genes?

In some samples of the monkeypox virus, large chunks of the genome seem to have disappeared or moved to entirely different spots in the sequence. It's too early to tell whether the mutations are beneficial, neutral or harmful to the virus. Scientists are monitoring the situation carefully to understand why the alterations have appeared, and what they might mean for the global monkeypox outbreak.

Crackdown at leading Iranian university

A crackdown by police and paramilitary forces at one of Iran's top universities has shocked academics worldwide. Student protests at the Sharif University of Technology in Tehran were part of widespread demonstrations triggered by the death of Mahsa Amini in police custody, after she was arrested on 13 September for not wearing her hijab correctly. On Sunday, students at Sharif fled security forces on or outside the campus, according to social-media videos and eyewitness accounts. "I feel extremely disturbed by the brutality and violence," says economist Farid Farrokhi, who works in the United States and studied at Sharif. "They are the future of Iran."

'I never imagined that I would be a farmer'

In response to the pandemic, US epidemiologist Brandon Brown sold his house and moved with his family to a small farm. "I knew things wouldn't end quickly," he says. "I wanted more outside space to grow my own food and be able to physically distance myself." Now responsible for hundreds of fruit trees and a flock of chickens, the newly minted professor had to find a way to achieve a more balanced life.

Dogs and people treated side-by-side

At a cancer research centre in Virginia, veterinarians and physicians work together to develop therapies for canine and human use. For example, researchers are testing brain-cancer treatments in dogs and then will test the same approach in humans. "It just so happens that the molecular, genetic, clinical similarities of canine and human brain tumours is pretty remarkable," says veterinary neurologist John Rossmeisl. "I got into the field to develop therapeutics to help dogs, and I can also simultaneously help people."