> we share about half our DNA with bananas.

I’ve seen this claim before. Where does it come from?

Humans have 23† pairs of chromosomes covering 21 thousand genes; bananas have 11 pairs, triplets, or quads†† covering 36 thousand.

† Usually, but there is a surprisingly high frequency of different chromosome counts

†† I only found out about triploid and tetraploid chromosomes today, don’t expect me to know anything

It's because genes are highly conserved, and I should have been more precise: we share about 50% of our genetic code with bananas. Intuitively this makes sense, since genes code for proteins and we can eat bananas (which can in turn eat us, with some help).

If you count the exome, which is not highly conserved because it doesn't play much of a role that we know of other than coiling, it's more like 1%. So "50% of our DNA" is not accurate, it's our genes.