African Americans have an extra leg tendon, you say?

I dislocated my kneecap recently and now spend multiple hours a week in physical therapy. Today while I was on one of the machines, I started talking with J, the receptionist, about subtle forms of racism within the LGBTQ movement because she asked me about what kinds of conversations I had at the NGLTF conference. I brought up the idea that lots of people expect every African American man on a college campus to be there to play sports as one example and asked rhetorically why people thought that. J responded, "Because of genetics." I waited a second before I realized she wasn't joking and then we had a fairly coherent conversation about how that's not scientifically true. Despite what it said in J's physiology book, published admittedly 15 years ago, African Americans do not have an extra or longer tendon in their legs. In fact there is no biological basis for race. We talked briefly about how science has been used over the years to prove all kinds of things that we as human beings wanted to believe was so in order to justify certain worldviews. "Yes!" J nodded-- "Like evolution?" I was trapped. Besides I was leaning against a rubber ball on a wall and kind of thought my legs might fall off, so I said "Maybe, kind of" and left it at that.