Human bodies have developed much differently compared to the bodies that we possess. The world full of vore and quick life cycles has caused the human body to change and adapt, not only to be able to successfully vore other individuals, but to adapt to the population difference and the issue of running out of prey. The human body however is a wonderful thing, adapting to all situations it is put under, allowing it to do what it needs to do to survive, and in a world where people swallow each other whole, the body is going to need to do some extremely heavy adapting to not only survive the world, but to be able to consume in the world as well. Most people couldn't originally consume others when the world government brought in the new rules surrounding it, but this was very quickly changed.
Female bodies first diverged from normality very quickly after the world government first formed. Injections of chemicals and other substances were given as vaccines, which was only given to women, while claiming for some plain old flu, rather it had the chemical imbalances to allow the human body eat another human body whole. The solution had two main elements. First, it changed how the human body perceived other humans as well as themselves. It removed bodily inhibitions, allowing the body to think it can achieve any active feat, allowing the Jaw unhinging that allows the swallowing of people to occur, as well as allows the body to digest the large amount of matter taken in during this ordeal. The second main element was the genetic passing gene, where these evolutionary changes would become part of that of which was passed down to young, to allow the cycle to continue without further of these injections, allowing it to make sure that all females had the chance to become predators.
This is due to the fact that the injections and furthermore the genetic trait passed down did not have a guarantee of success, rather it had a chance to allow a predator to be born from an individual. With a so-so success rate, this was partially due to a gene issue that wasn't tested for, though those in the highest power well know this was deliberate to make sure that the edible population didn't decline overly quickly. Those who were not predators still gained some of the effects of the gene change, but not the ability to consume. Of course, this meant that individuals who couldn't consume could still pass the gene onto their children without issue, meaning the cycle could continue easily.
There were many side effects of this however. First off, anyone that was classified a predator was much stronger than any non predator, meaning that women easily became the dominant gender of the planet due to their largely overpowered strength, however the amount of females declined quite rapid when the chemicals were introduced, as another side effect of the concoction was that birth rates for the genders became extremely skewed. Males were being born ten to one to females, while originally considered a mistake, this too was a flaw by design, to make sure the edible population stayed high, plus to attempt to keep some level of gender balance within the world. The final main thing that the concoction did was make pregnancy times drop drastically, having a child only take a third of the time to develop and be born than those before such a thing was introduced.
Those who do not become predators gain the increased pregnancy speed as well as gene passing and the skewed birth rates, nothing else was ever given to those who could not become predators. But there is one thing these individuals have, a genetic disposition that allows these individuals to under extreme circumstances or extremely lucky circumstances, birth a Male predator. These individuals are beyond rare, and most usually get eaten before they realize their predatory nature, but those that awaken their predatory nature are known to be some of the most dangerous individuals in all world, being even stronger than female predators and more hungry.
While not related to the injections, other things have changed about human physiology, such as the stomach, which has now evolved to take in large quantities of food much more easily, as well as females growing up much more voluptuous due to the lack of fatherly pheromones to keep their sexual development quelled (before you ask, yes, this is a real thing, look it up.), since most fathers were eaten during pregnancy or eaten by the very young they had helped create.
