1938 – 2011 · A portrait
A biologist who said the cells of every plant and animal were built out of mergers — and was laughed at, until the evidence arrived.
The line above is how her claims were received — by the scientists whose job was to doubt them. It rises as a claim is tested and accepted, and the room brightens with it. It is not a verdict on truth: some accepted ideas are later overturned, and some rejected ones come back. A hollow point is a claim still open.
She argued that the parts of our cells that burn oxygen were once free-living bacteria — swallowed by another cell, and never digested. The paper was turned down by about fifteen journals before one printed it in 1967.
She expanded it into a book, and the reaction ranged from polite disbelief to open ridicule. Cells were thought to evolve by slow mutation, not by one organism moving into another. The idea wasn't new — a Russian botanist had proposed it in 1905 — but she was the one who wouldn't let it go.
The tools caught up with her. Both mitochondria and chloroplasts were already known to carry DNA of their own; now sequencing showed whose it was. Chloroplasts matched cyanobacteria. Mitochondria matched another group of bacteria. The guests had kept their papers.
Within a decade the theory was in the textbooks, and it is there now. Elected to the National Academy of Sciences in 1983; given the National Medal of Science in 1999.
She pressed further: that merging, not mutation, is how most new species arise. Most biologists remain unconvinced. So a new line begins, apart from the first — a new claim has to earn its own place.