stages of the creation of man

Till, when he (the traveller Zul-qarnain) reached the setting-place of the Sun, he found it going down into a muddy spring (18:86)

"Let us divide the creation of the foetus overall into four periods of time. The first is that in which, as is seen both in abortions and in dissection, the form of the semen prevails ... But when it has been filled with blood and heart, brain and liver are still unarticulated and unshaped yet have by now a certain solidarity and considerable size, this is the second period; the substance of the foetus has the form of flesh and no longer the form of semen. The third period follows on this, when, as was said, it is possible to see the three ruling parts clearly and a kind of outline, a silhouette, as it were, of all the other parts. You will see the conformation of the three ruling parts more clearly, that of the parts of the stomach more dimly, and much more still, that of the limbs. Later on they form "twigs", as Hippocrates expressed it, indicating by the term their similarity to branches. The fourth and final period is at the stage when all the parts in the limbs have been differentiated; and at this part Hippocrates the marvelous no longer calls the foetus an embryo only, but already a child, too when he says that it jerks and moves as an animal now fully formed".
[Corpus Medicorum Graecorum: Galeni de Semine (Galen: On Semen) (Greek text with English trans. Phillip de Lacy, Akademic Verlag, 1992) section I:9:1-10 pp. 92-95]

In this book I have considered only established scientific facts and not mere hypotheses and theories that are based on assumptions and are not backed by proof.