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Where Babies Come From
Historians: Contemporaneous documentation of the initial events is often sparse, and in fact people often get testy and uncooperative when we urge better documentation for the historical record.
Title text: Historians: Contemporaneous documentation of the initial events is often sparse, and in fact people often get testy and uncooperative when we urge better documentation for the historical record.

Explanation

Children are often curious, and ask a lot of questions about the world around them. "where do babies come from?" is one such question that tends to come up at some point, and is notable as one that many adults are uncomfortable giving correct answers to, because of the common reluctance to discuss sex-related matters with youngsters. While children are sometimes told that there's a baby inside a pregnant woman's tummy, the issues of how the baby got in there, or how it's supposed to get out, are often dodged. There are a variety of common myths about where babies come from, as told to children, such as "brought by a stork", "found in a cabbage patch", or "built from a kit". This comic presents a variety of answers to that question, supposedly from the point of view of specialists in several different areas of science, some of which are incorrect, others of which are allusions to the process of conception or childbirth expressed in the vocabulary of the specialist's field.

They might be deliberately misleading the questioner by using very euphemistic terms to avoid personal embarrassment, deliberately over-'simplifying' the explanation as a stepping stone to the eventual more specific truth, or else they are themselves ignorant/misled about the process. In each case, however, their abstraction of the process is described in terms that are actually relatively technical ones from their own field, to the presumed audience, showing that they are not necessarily able to find the right level of explanation, as well as not having used a less obtuse reframing of the topic much closer to that of actual reproductive biology.

Geneticist
An admixture event refers to new genes being introduced into a population (for example, intermarriage adding genes for blue eyes into a population that previously lacked them). These gene movements are typically measurable on the order of thousand year or more timescales, and therefores are commonly dated to thousands or even millions of years ago. KYA = "one thousand years ago" and 0.001 KYA = 1 year, approximately the duration of most human pregnancies. The comic uses this term to describe the gene mixing of two people having a child. The joke is in the use of such large scale terms to describe the creation of one child, and how the technical language being used hides the answer, especially from a child.
Astronomer
Ejections of matter from parent bodies are common astronomical events, at scales ranging from comets to black holes. The process of giving birth is compared to a "low-impulse" ejection, such as the casting off of rocks and dust from a rotating asteroid. Such a comparison, while it may make sense in cosmology, is unlikely to find favor with any woman who is, or has ever been, in labor.
Alternatively, the "low-impulse ejection" could refer to ejaculation, not the act of giving birth. The former would have a considerably higher impulse than the latter but it's still very low on a cosmic scale and would still qualify as "low-impulse".
Software Engineer
An off-by-one error (aside from being a difficult theme to build a party around) is a common programming mistake in which a value is, well, off by one. A birth could be described as a "population" metric increasing by one, or alternatively, a baby could cause a previously accurate static population metric to become off-by-one from the new reality of the situation. This could also be referring to an unplanned pregnancy, which would lead the local population to be one higher than the parent(s) may have calculated.
Geologist
The baby is said to have been created by the process of differential erosion, in which softer rocks are eroded more quickly, leaving harder rocks behind. Arguably, a geologist who was making a serious attempt to compare geological and biological processes would recognize that the growth of a fetus has much more in common with accretionary, rather than erosional, mechanisms. Granting that the geologist depicted is witty and not clueless, this explanation is the most intentionally farcical, the most Calvin's Dad, of the five. The suggestion that everything is removed except for the desired result is fairly often used to describe how sculptors work, and similar craftspeople such as woodcarvers.
Meteorologist
Turbulent mixing of air masses ("turbulence") has been experienced by just about everyone who has ever been in an airborne aircraft. Turbulence can occur at all levels of the atmosphere from the ground up, and is frequently accompanied by clouds and precipitation, although the moisture alluded to here is likely that of bodily fluids and the turbulence being more about a tangible physicality between people. It is a pungent metaphor for coitus.
Historians (title text)
Instead of proffering an explanation for "where babies come from", the historians (plural) lodge a complaint about the difficulties they have encountered in obtaining the data needed to substantiate the babies' provenance. The plaint is a common preamble and disclaimer in formal history publications. Rather than answer the question in the general, they appear to be trying to answer it for each individual baby by questioning those thought to be responsible. The historians express surprise and indignation that their efforts to obtain "better documentation" of the "initial events" (the mating behavior) leading to baby formation are seen as prurient and voyeuristic, and are met with resistance.

Transcript

[Hairy, Ponytail, Hairbun, Cueball and Megan are standing below a question given at the top of the comic. Each of the five gives their answer to the question. Below each character is a label with their respective occupation.]
Various experts answer the question “Where do babies come from?”
Geneticist
Hairy: Recent admixture event, roughly 0.001 Kya.
Astronomer
Ponytail: Low-impulse ejection from a parent body.
Software engineer
Hairbun: Off-by-one error in the population calculations.
Geologist
Cueball: The area was originally a uniform plane, but the non-baby parts eroded at higher rates.
Meteorologist
Megan: Moist ground-level turbulent mixing.


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