John Macfarlane was the first to recognize Eukaryota as a group

To the Editor — Of all three primary evolutionary groups (domains/empires) of life¹, the recognition of eukaryotes (organisms with nuclei in cells) as a distinct systematic group was the earliest^2,3,4,5. Numerous micro- and macroorganisms are eukaryotes. They comprise animals (humans included), plants, fungi and diverse (predominantly micro-) organisms collectively called ‘protists’. The person most often credited with recognition of eukaryotes as a group is Édouard Chatton (for example, refs. ^1,2,4).

Photo of John Muirhead Macfarlane taken by Frank Morton Jones (1869–1962) and available from the Harvard Forest Library.

In 1925, he twice mentioned the grouping called ‘Eucaryotes’, without clarification, in a report on a protist species^2,3,4. The first time Eucaryotes contained only protists, and the second time animals and plants were added^2,3. Thus, his paper left us with the unexplained etymology of the name, two contradicting circumscriptions and the impression that the group had been introduced before.

To my regret, I found no publications that mentioned that this actually was done before, and that Chatton, despite the rest of his excellent scientific achievements⁴, was only a rediscoverer (reproducer?) here.

In 1918, the Scottish-American scientist John Muirhead Macfarlane published the book entitled The Causes and Course of Organic Evolution⁵. In chapter III, he divided all life into Acaryota and Caryota. He repeatedly used these taxa discussing evolution throughout the book and included in Caryota all organisms, whether uni- or multicellular, in which cells contain nuclei. The definition was brief and unambiguous: “nucleate organisms” (page 51 in ref. ⁵).

Although the name and taxon Acaryota were already introduced by Ernst Haeckel in 1894 (page 52 in ref. ⁶), the taxon Caryota was introduced by Macfarlane. While he recognized the group correctly, Macfarlane had misconceptions about it. He thought that the nucleus originated more than once in the course of organismal evolution (tipped-in figure between pages 474 and 475 in ref. ⁵) and introduced the taxon Caryota as an evolutionary grade. Also, he (like Haeckel before him) erroneously placed a portion of protists in Acaryota because the nucleus was not then observed in them. Similarly to Haeckel’s Monera, Macfarlane’s Acaryota were defined negatively: “non-nucleate organisms”. Nevertheless, his definition of Caryota is positive, unequivocal and results in the content coinciding with Eukaryota in their current sense.

The status of the nucleated–non-nucleated divide inventor was assigned to Chatton largely due to a combination of social circumstances. When Roger Stanier and Cornelis Bernardus van Niel came to the importance of this divide, they conversed with André Lwoff, Chatton’s former pupil, who made them aware of Chatton’s publications on the subject and the names he used for these groups².

In 1963, the prokaryote–eukaryote divide was famously called “the greatest single evolutionary discontinuity to be found in the present-day world”⁷. The later development of our knowledge of the evolution of life smoothed this sharp difference. Perhaps the biggest discovery in the history of life of the later twentieth century was the recognition of Archaea as a distinct group¹. In this way, light was shed on the paraphyletic nature of prokaryotes. Recent studies have indicated the paraphyly of Archaea in its turn⁸. At the same time, the group of nucleated organisms (Caryota/Eukaryota) has not weakened over the century. It has strengthened, if we take into account Macfarlane’s original view on its origin.

During his lifetime, Macfarlane was mainly a botanist and held a professorial chair at the University of Pennsylvania (United States) after his education at the University of Edinburgh (United Kingdom) and occupation of various academic positions there and at the Royal Dick Veterinary College⁹. At the University of Pennsylvania, he played a leading role in organizing and diversifying its botanical garden⁹. Also, he encouraged women to do science¹⁰ at a time when doing so was uncommon.

Now, Macfarlane is generally forgotten. He did not live long enough⁹ to see the surge of interest in nucleated organisms as a taxon² and was deprived of the opportunity to remind humanity of his work. At the same time, the traditional taxonomic principle of priority provides grounds for changing the official name of eukaryotes (Eucaryotes/Eucaryota/Eukaryota/Eucarya/Eukarya) to Caryota Macfarlane 1918. I would note, however, that there is no generally accepted nomenclatural code that governs taxa of such high rank and could either prescribe or forbid this amendment.