Haeckel 1912 and the gibbon to human hypothesis

When paleonanthropologist Christopher Bae,
discussed human origins on YouTube (Evolution Soup), he reported @10:25 that Ernst Haeckel, “suggested that if we’re going to look for the quote-unquote missing link, it’s probably going to be between man and ape. It’s probably going to be someplace in SE Asia. And part of the reason for this is, he argued that we are more closely related – keep in mind this is the 1800s time period –  we are more closely related to gibbons.”

At that, I went down the rabbit hole, searching for the source for Bae’s quote.

Recent support for a gibbon-human interrelationship (Fig 1) is online here

Bae continued,
“Gibbons are generally monogamous. And when they are on the ground they actually walk bipedally.”

Exactly! Then Dr Bae dismissed the notion.

Question is: What is the citation (if there is one) that put gibbons on this pedestal?
And when was it removed? Back to the rabbit hole…

Ernst Haeckel, ‘the father of phylogeny.’
I connected Haeckel with engravings of embryos. I did not realize how closely his publication, ‘The Evolution of Man’ paralleled my own publication from 1991, ‘From the Beginning, The Story of Human Evolution.’ In it 36 steps were presented. Haeckel wrote, “Next to the lemurs come the true apes (Simiæ), the twenty-sixth stage in our ancestry. “

That coincidence is uncanny.

On a side note, re: the placenta, Haeckel wrote,
“Some of the Marsupials (Perameles) have the beginning of a placenta. In some of the Lemurs (Tarsius) a discoid placenta with decidua is developed.”

The bandicoot, Permales has a pouch that opens to the rear. The placenta, such as it is, has no villi (= small slender vascular projections that increase the surface area of a membrane). See Howe 1896, Hill 1897 and Flynn 1923. Nothing more recent.

So that makes a fourth or fifth origin for placentation in the LRT.

The decidua is a specialised, highly modified endometrium that develops during pregnancy. The form of the human placenta is generally classified as a discoid placenta. Within this, the cotyledons are the approximately 15-25 separations of the decidua basalis of the placenta, separated by placental septa. Each cotyledon consists of a main stem of a chorionic villus as well as its branches and sub-branches.

On another side note, re: placentals, Haeckel wrote,
“The four great legions of the Placentals—Rodents, Ungulates, Carnassia, and Primates—are sharply separated to-day by important features of organisation.”

This is roughly how the LRT divides basal placentals.

On another side note, re: lemurs, Haeckel wrote,
“They are of different kinds. Some are closely related to the Marsupials (especially the opossum). Others (Macrotarsi) are nearer to the Insectivora, others again (Chiromys) to the Rodents.”

The LRT does not confirm this hypothesis. Even so, lemurs are not far from the Virginia opossum (Didelphis) in the LRT.

Worth noting: taxonomists back then as they do now, were inventing new clades and dismissing/ignoring others. It gets historically confusing.

Getting back to gibbons,
Haeckel gave credit to another author, Klaatsch, in this manner, “He says explicitly (p. 172): “The three anthropoid apes—gorilla, chimpanzee, and orang—seem to be branches from a common root, and this was not far from that of the gibbon and man.”

Unfortunately, that’s as close as Haeckel 1912 gets to linking gibbons and humans.

Haeckel settles the issue,
“The gorilla comes next to man in the structure of the hand and foot, the chimpanzee in the chief features of the skull, the orang in brain development, and the gibbon in the formation of the chest. None of these existing anthropoid apes is among the direct ancestors of our race; they are scattered survivors of an ancient branch of the Catarrhines, from which the human race developed in a particular direction.”

So Haeckel’s answer in 1912 was ‘none of the above’.

I now wonder where Christopher Bae got his notion about Haeckel’s gibbon hypothesis?

References
Flynn TT 1923. The yolk-sac and allantoic placenta in Perameles. J Cell Sci s2–67(265):123–182.
Haeckel E 1912. The Evolution of Man. A popular scientific study. Watts & Co, London. Translated by McCabe J. Read it online here. Read our ape ancestors here.
Hill JP 1897. The placentation of Perameles. J Cell Sci s2–40(159):385–446.
Howe GB 1896. Marsupial with an allantoic placenta.
Klaatsch H 1923. The evolution and progress of mankind. London: T. Fischer Unwin Ltd
Peters D 1991. From the Beginning, The Story of Human Evolution. Wm Morrow.  online here

wiki/Hermann_Klaatsch
wiki/Ernst_Haeckel

Source: https://pterosaurheresies.wordpress.com/2024/12/24/haeckel-1912-and-the-gibbon-to-human-hypothesis/