The science of the nineteenth century was dominated by the perfectibility of knowledge. Fueled by the analytic/systematic distinction provided by Kant, the European thinkers of the day were bent on elucidating all the empirical rules that governed the universe. Even if the universe was infinite everything was potentially knowable and humans were capable of detached observation that could elucidate and name all these facts and rules.
In terms of development mammals are weird. We have clearly evolved a set of wacky adaptations to allow us not only to mature entirely within the parent, but also to do so without the huge supply of yolk common to most other animals. Think of your regular egg. That big ball of yolk is covered by a single plasma membrane and provides everything that chicken needs for the roughly twenty-one days it takes to go from laying to hatching. As a freaky aside, that entire chicken (if fertilized) will grow from a small white mass (the blastodisc) visible on every single store-bought egg. Mammals, not having that whole bunch of rich and yummy stuff to eat in the weeks it usually takes them to develop, instead do a whole bunch of crazy things for which there is no real comparison elsewhere, except that a lot these structures (the amnion and alantois) are also present in the the eggs of birds and reptiles. What we’ve got here is a whole suite of adaptations used grow new organisms on land, which would be completely mind-boggling if you didn’t consider the 600 million years (that’s 219 billion days, to put it in perspective) that it has taken these systems to develop to their current state.
There are a number of ways the soul, a theoretical conundrum as indemonstrable as the creator herself, could have come to be. Ernst Haeckel tells us that it’s not taken a bit from mom and a bit from dad, nor does it lie in wait until called upon, and it’s not a germ passed from Adam on down. It just is, and arises as such at the moment of fertilization, not coitus. While this strangely drawn argument could collude with certain anti-abortion sentiments, it is actually from the mind of man who considered himself a staunch liberal and free-thinker. Darwin’s champion in Germany, lover of that compounding of words so fancied in German, is credited with first identifying the kingdom Protista and coining the terms ecology, phylogeny and ontology. A vexing character whose books on evolution far outsold Darwin’s Origin and Descent of Man, Haeckel was lambasted by Stephen Jay Gould for his “irrational mysticism” who also characterized Haeckel’s science as “dogmatic, unfounded and distinctly non-Darwinian.”