The year humans lost a pair of chromosomes

Scientists, supposedly, live and die by facts and data. This was a doctrine I received at a very young age and was extremely surprised when I first got into this business when I realized that scientists are just people and extremely fallible. The “scientific process” is very slow, often taking decades if not centuries to correct bad knowledge. I used to think that wrong interpretations were a result of limitations in technology – if we only had THAT device, we could have corrected that earlier. The reality is more dastardly: many mistakes in science persist because the creators of wrong knowledge refuse to acknowledge their mistakes and often intimidate others (with correct information) from positions of power. This phenomenon has lead a once well known practitioner of the trade to remark “Science advances one funeral at a time”.

I still get surprised when I learn about examples where a researcher had correct data, arrived at the correct conclusion but discarded it (or was forced to discard it) because it went against dogma. I had read about the Millikan experiment in Feynman’s surely you are joking book (It was part of a commencement address he gave.) This is perhaps the most well known example of biases in science holding things back, but in a way this particular error was tiny (at least in my world view, physicists are used to arguing about things to many more decimal places).

What prompted this post was me recalling this phenomenon while reading “Essential Genetics” by Hartl and Jones. In the chapter on Gene Linkage and Genetic Mapping there is an excerpt (and editorial) from a 1956 paper by Tijo and Levan that states that up until then it was widely believed that humans had a chromosome number of 48, just like chimpanzees and gorillas. That’s not the bad part – we often have incomplete or wrong information.

Here’s the galling part: a previous researcher (Hansen-Melander) had previously led an experiment where the researchers had repeatedly found 46 chromosomes in human samples. Instead of reporting this, they decided the experiment was borked and stopped it, because they could not find the “correct” number of human chromosomes.


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