THE CONSTRUCTION OF MAN’S 
FAMILY TREE. 
BY 
SIR ARTHUR KEITH, F.R.S. 
SomEwHERE about the year 1865 Ernest Haeckel, the young and enthusiastic professor 
of zoology in the University of Jena, did an unprecedented thing ; he drew a family 
tree to represent man’s relationship to the rest of the animal kingdom. It will repay 
us to review the circumstances which led Haeckel to make this bold attempt—the 
first of its kind—to represent man as a sprig on the great tree of Life. The essential 
circumstance was the appearance of Darwin’s Origin of Species at the close of 1859 ; 
Haeckel was then a young medical man, aged 25, investigating marine forms of life 
in the zoological station at Naples. A subsidiary circumstance, still a very important 
one, was the appearance of Huxley’s Man’s Place in Nature in 1863. By then Haeckel 
was established in the University of Jena. Neither Darwin nor Huxley were so 
daring as Haeckel. Even in 1871, five years after Haeckel had published his Generalle 
Morphologie, with its wealth of pedigree tables, Darwin, in his Descent of Man, went 
no further than to infer that ‘a member of the anthropomorphous sub-group gave 
birth to man.’ As to the date of that event, he would not commit himself because of 
lack of evidence. It might have been ‘as early as the Eocene,’ he admitted ; all he 
was assured of, on the evidence then available, was that ‘in the upper miocene the 
great and small anthropoid apes had already diverged. Huxley in 1863 was equally 
cautious. He drew no pedigree. The utmost he adventured was the opinion that 
man had arisen by ‘the gradual modification of a man-like ape or from the same stem Be 
As to the date of man’s emergence he was caution personified. _‘ Time will tell’ was 
all he said. But he was prepared to find the fossil remains of Homo sapiens in strata 
of pliocene or miocene date, or even in those of an earlier period. Where Darwin 
and Huxley feared to tread the young and daring Haeckel, pioneer and prince of 
pedigree-makers, stepped boldly in, and if he blandered, it is not his error which 
impresses us to-day but the amazing degree of his success. Where in the modern 
world is there a man with sufficient knowledge and courage to reconstruct the entire 
tree of life single-handed? Yet that is what Ernest Haeckel did between 1864 and 
1866—just after he had attained his thirtieth year. 
What made Haeckel so bold? It was this. The doctrine of evolution, as 
expounded by Darwin, presented itself to Huxley’s cool judgment as an acceptable 
working hypothesis; to Haeckel’s glowing and penetrating imagination it came as 
a revelation of reality. He immediately saw life as a great tree rooted deeply in 
the geological past with trunk and great branches dead, buried and fossilised, only 
the end-twigs peering through the surface of the earth into the present as living forms. 
Convinced of its reality he immediately set to work to reconstruct that tree. Only 
one branch of Haeckel’s tree concerns us to-night—a branch on the extreme right 
of the tree—a branch which represents the order to which man belongs—-the Primates. 
The terminal twig on the extreme right represents humanity (Homo sapiens). 
Haeckel’s tree had a storm-blown appearance; its branches, under the stress of 
evolutionary winds, tended to grow in one direction—the most progressive branch 
of all—the human branch, occupying, as it should do, the extreme right. We are 
surprised to note how closely he has set the twig or branch which gave birth to the 
African anthropoids—the gorilla and chimpanzee—to that which eventuated in man; 
all three are made to emerge from the same terminal stem. When we follow this 
human-gorilla stem towards the left and downwards—that is, against the stream of 
progress and of time—we find shooting from it the orang twig; then, at a still longer 
interval, the gibbon branch; then a long way further to the left the old-world monkeys 
emerge, then those of the new world; ultimately, this primate stem, after moving 
far to the left, merges with the stem of the prosimiae or lemurs. 
1931 NN 
