Neil deGrasse Tyson’s recent tweet about ‘painful’ animal sex has sparked criticism, with experts questioning his grasp of biology.

“If there were ever a species for whom sex hurt, it surely went extinct long ago,” the astrophysicist tweeted to his 5 million Twitter followers Friday.

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The Internet was quick to pounce on the tweet, with experts citing examples of animals that experience painful sex. “Yeah I’m sure female cats *love* those spined cat penises. Oh and bedbugs can’t get enough traumatic insemination,” tweeted Nerdist science editor Kyle Hill.

@neiltyson Yeah I’m sure female cats *love* those spined cat penises. Oh and bedbugs can’t get enough traumatic insemination. — Kyle Hill (@Sci_Phile) March 11, 2016

Other members of the science community also poured scorn on deGrasse Tyson’s comment.

I really love NDT & he was lovely to me when we worked together, but his grasp of biology is frequently flawed. :/ https://t.co/FfnfRrZ5r3 — Mika McKinnon (@mikamckinnon) March 11, 2016

Apparently enjoying the brouhaha over his animal sex tweet, deGrasse Tyson took to the social media site again on Saturday. “I think I’ll try out one more on the biologists...,” he tweeted. “If you have a gene for celibacy, you didn’t inherit it,” deGrasse Tyson added, in a subsequent tweet.

The astrophysicist is no stranger to duking it out on Twitter, as evidenced by his high-profile ‘flat earth’ row with rapper B.o.B earlier this year.