It's more that Darwin does. A fat binary is just two independent Mach-O binaries concatenated with a small header.

Maybe, but ELF doesn't support doing so

One might be interested in the not-very-alive FatELF implementation, though: https://icculus.org/fatelf/

	▲	yjftsjthsd-h 7 hours ago \| parent [-]
		Yep, that sounds like the same idea: > The format is very simple: it adds some accounting info at the start of the file, and then appends all the ELF binaries after it, adding padding for alignment. The end of the file isn't touched, so you can still do things like self-extracting .zip files for multiple architectures with FatELF. But I would indeed call it very-not-alive; their demo image is Ubuntu 9.04