An earlier commenter recommended Richard Wrangham’s work, including his text, ‘Catching Fire: How Cooking Made Us Human’ (2010). That’s an excellent summation of his ideas!

Richard Wrangham’s work is definitely seminal for how cooking influenced our evolution from about 2 million years ago- cooked foods might be exactly why the brain is 33% larger from Homo erectus onwards, and why the jaw reduces just as swiftly. But for the last 10,000 years, it’s also the impact of domesticated foods and eating ever-softer foods that’s impacted our jaw and teeth morphology. This article discusses nutrition shifts from both millions of years ago, and thousands of years ago: Luca, Perry, and Di Rienzo 2010, citation below and linked here: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4163920/

As to why our teeth and jaws are a bit off-kilter to each other: treat each of them like two sets of traits (skull size vs. teeth size). We’ve eaten softer foods from at least the last 10,000 years, so both our skulls and our teeth have gotten smaller- but teeth lag behind the skull.

Change in traits over time is tricky. Change in the morphology of any trait is partly dictated by the environment, and partly by genetics. On the genetics side, that includes the rate at which mutations are passed on from prior generations. On the environment side, influences include the foods we eat, minerals in water we drink, overwork and strain, crowded housing and spread of diseases and parasites, etc.

When we’re talking teeth changes, and whether the upper and lower teeth line up with each other (and wear on the tips, as opposed to an overbite/underbite situation), there’s two major things at play: the size of the teeth, and also the size of the skull (including the jawbones). For sanity’s sake we can lump these into two traits: skull size, and teeth size, though savvy readers will note that each would actually be a cluster of different traits.

Some traits are more strongly dictated by genetics than the environment. That’s the case with teeth. When this happens, the trait is more resistant to environmental influence, and changes manifest more slowly in that trait. The impact of the environment is slowed down a bit because traits inherited from previous generations hold back changes a bit more.

(The impact of the environment on traits isn’t exclusive to genetics for a number of reasons: bone anchors muscle, and muscles that are worked more often impact the bone, because bone changes throughout a person’s lifetime. Also, there’s critical periods of growth in childhood and adolescence, where the environment has a greater influence by impacting how the bones grow and shape at those times in our lives. For example: people who grow up in high altitude regions [like the Andes] have expanded chest cavities because the environment impacts the shape their bones take when they’re in that region during times when the bone is growing.)

To explain why genetics dictating traits would work more slowly, if anyone’s interested: Mutations occur all the time, but they’re only passed on to later generations if the mutation occurs on the gametes (sperm and egg cells). To do that, the mutation has to be on the segment of DNA that’s actually passed on to the sperm / egg cell (and its halved number of chromosomes) after meiosis (which shuffles the genes, so that each egg or sperm cell you’ve got is an unique combination of different bits of each of your parents’ DNA). Some of your sperm/egg have the mutation, and some of your sperm/egg cells don’t, since each sex cell only has half of your DNA. …If I’ve lost you here, it’s okay. Genetics isn’t everyone’s preferred cup of tea.

Skull size and teeth sizes are each dictated by both: genetics and the environment. But skull shape is slightly more influenced by the environment (foods we eat), while teeth are more dictated by genetics. So the rate by which the skull has changed size and shape in the last 10,000 yrs is slightly faster than the rate by which the teeth have changed size.

The article linked above discusses several broad shifts in human diet over our evolutionary past; the citation is: Luca, Perry, and Di Rienzo. 2010. Evolutionary adaptations to dietary changes. Annual Review of Nutrition 30: 291-314.

Another super interesting topic is how our mouth morphology changes over time have impacted the actual sounds that our mouths make; sorry, can’t give you a more academic source just now because it’s the holidays and there are kids about to run loose: https://www.smithsonianmag.com/science-nature/ability-pronounce-f-and-v-sounds-might-have-evolved-along-human-diet-180971710/

Edit: spelling