Lindsey Ellefson is Lifehacker’s Features Editor. She currently covers study and productivity hacks, as well as household and digital decluttering, and oversees the freelancers on the sex and ...

It’s called Biomate. I ran across an ad for it in a magazine from the 1970s and had no idea what I was looking at. For a while in the 1970s, these charts were everywhere. Las Vegas bookmakers like ...