Psychology
We Can Only Maintain ~150 Friendships
Robin Dunbar found that the human brain can maintain stable social relationships with roughly 150 people at once — a figure now called "Dunbar's number".
Science
Honey Never Spoils
Archaeologists found 3,000-year-old honey in Egyptian tombs that was still edible. Honey's low moisture and acidic pH make it inhospitable to bacteria.
Science
Octopuses Have Three Hearts
An octopus has three hearts: two pump blood to the gills, while the third pumps it to the body. When swimming, the body-heart stops — which is why octopuses prefer crawling.
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