DEVELOPMENT OF THE HUMAN BEING 
We might mention also the soft woolly hair called 
lanugo which covers the human fetus at a certain age, but 
is shed prior to or soon after birth. Numerous other tran- 
sient similarities to other forms of life have been detected 
in the human embryo. Some of them even persist through 
adult life. So many and curious are they that they have 
given rise to what is called the “doctrine of recapitula- 
tion.” This is the idea that in the development of each 
human individual from the germ-cell to adult life we see 
recapitulated in a fragmentary way the organic evolution 
of man’s entire ancestry. Organs which it is suggested 
were functional in man’s remote animal ancestors, but 
under present conditions are useless, briefly show them- 
selves, and by disuse atrophy and are lost. Some, indeed, 
like the hair and vermiform appendix, are in process of 
being lost, although in earlier ancestral forms of life they 
were valuable functionally. 
It is, of course, perfectly obvious that, in the skeleton; the 
skin; the lungs and their accessories; the heart and the 
blood circulation; the digestive and reproductive organs; 
and in many other particulars, man bears a strong re- 
semblance to many of the mammals, and more particu- 
larly to the great apes. It is stated by Sir Arthur Keith! 
that only thirty per cent of man’s structural details are 
peculiar to himself and not shared with any others of the 
primates. Among the remaining seventy per cent there 
are said to be twenty-six per cent of characters which man 
shares with the gorilla or the chimpanzee but with no other 
animal. Going back to other genera of the primates, there 
are found eight per cent of characters shared by man and the 
great apes with the gibbons, and indeed a small residue of 
characters shared with the little monkeys of South America. 
Such facts and considerations as these, added to those 
outlined in Chapter II, have led most anthropologists to 
admit great probability in the hypothesis that man is not 
an independent creation but a gradually developed animal 
1See Encyclopaedia Britannica, Ed. 13, vol. ii, p. 779 
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