Biology

Search this and you get a list. Rodents, rabbits, birds, insects, earthworms, berries, carrion, and whatever fell out of your bin. Every source has the same list because the list is correct. It is also useless, in the way that a list of things a car can run into is useless if what you wanted to know was how fast it goes. I wanted the number. How much food does a fox actually need, in a day, and what does that imply about how it spends its time? The answer turns out to explain the list. ...

I asked whether intelligent life on another planet would follow anything like our evolutionary path, or whether humans are a one-off. Everybody who answers this question reaches for the same argument, and I reached for it too before I checked it. It is a good argument. It is also, in the specific form everyone uses, wrong. The argument everybody makes Evolution repeats itself. Give it the same problem twice and it finds the same answer twice, so the features that keep reappearing on Earth are the features we should expect anywhere. ...

You have heard this one. Every seven years, every cell in your body has been replaced, so you are a physically new person, and the coffee stain you feel guilty about was technically spilled by somebody else. It is a lovely thought and it is not true. Some of the cells reading this sentence have been with you since before you were born. We know that with unusual confidence, and the reason is grim and wonderful. Between 1955 and 1963 the world tested nuclear weapons in the atmosphere, and in doing so accidentally wrote a date stamp into every living thing on the planet. ...

Last October I asked whether you could engineer a human, or any mammal, to run on sunlight the way a plant does. I expected a biology answer, something about genes and organelles and immune rejection. What I got was arithmetic, and the arithmetic ends the argument before biology gets a turn. The answer everyone gives is the weakest one Search this question and the first thing you will read is that humans cannot photosynthesize because we have no chloroplasts and produce no chlorophyll. ...

I asked a question I had heard the answer to a hundred times: is it true that half the cells in my body are foreign bacteria? The answer turns out to be yes, roughly. Which is strange, because the version everyone repeats is that bacteria outnumber your own cells ten to one, and that version is wrong. The numbers In 2016, Ron Sender, Shai Fuchs and Ron Milo went and did the arithmetic properly. For a reference adult male of 70 kg: ...