In turtles, heat decides sex. Most species don’t use chromosomes to determine gender—instead, it all depends on the temperature of the sand where eggs incubate. Cooler nests tend to produce males, while warmer nests yield females. As climate change heats up nesting beaches, researchers have documented entire populations where almost every hatchling is female.

And what about humans? Some scientists have observed slightly more female births closer to the equator, possibly due to temperature, sunlight, or environmental stability. The evidence is still debated—but it’s a curious hint that nature may play favorites based on geography.