i remember reading that higher calorie supply makes people more willing to breed, so agriculture kinda caused people to have more kids, because they could.

I don't believe infanticide was a common thing at any point.

For one, people in the past were well aware that some herbs had a dampening effect on fertility (not as comprehensive as modern methods, but still apparently visible emough). Together with a longer breastfeeding period and less nutrition, that will have been enough to curtail the actual amount of pregnancies.

People loved their children. There are enough grave inscriptions and stories detailing the depth of grief or framing a willingness to sacrifice your own kid as remarkable obedience (Abraham and Isaac, Cepheus and Andromeda). I see no reason to believe that this should have been so different in the cultures before recorded history.

Nope, that started after the neolithic revolution.

Before that, people had way less kids since 1. diseases weren't as rampant then as they were after beginning agriculture (turns out that living in close corridors and near your animals that are full of diseases and parasites may not be healthy), and 2. people breastfed their babies until 3-5 years, unlike later, when people only breastfed them for a year or so, or even used wet nurses, which allowed the mother to get pregnant again soon after giving birth.

Of course a lot of kids surely died, but not nearly as much as in later societies up until the introduction of vaccines and other parts of modern medicine.

As for infanticide, I'm not particularly knowledgeable on that, but I'm pretty sure that it wasn't nearly as common when births were much rarer and attitudes towards groups that later cultures usually killed as babies, such as disabled people, intersex people, and others that were considered 'deformed', were much more lenient.

do you have any sources for infanticide?

was infant mortality higher for hunter-gatherers compared to Neolithic or even medieval times?

some information from a quick search (i'm not an archeologist or anthropologist. I was just very interested in Neolithic period at some time 🤷

After the adoption of a sedentary lifestyle with a more steady supply of high-calorie foodstuff ensured by agriculture and animal husbandry, the birth rate increased and demographics changed. Better nutrition and reduced female mobility led to shorter intervals between births, and ultimately to a significant growth of the Neolithic population. This ‘baby boom’ is also known as the Neolithic Demographic Transition. Whether a shortened period of lactation is also a factor in this development, is currently under investigation in a project led by Sofija Stefanović from the University of Belgrade, Serbia. The availability of suitable weaning foods such as cereal grains might have enabled to wean babies earlier, which led to a quicker return of mothers’ fertility.

In the typical pattern of Neolithic societies, siblings are now born in quicker succession, leaving only two to three years between births. Farming communities are known for having many children – not only because they can be supported nutritionally, but also because their labour is needed for the plentiful work in the fields. The physical toll of childbirth probably increases for the mothers, and their social position may change significantly. If they no longer go out on gathering trips as much and remain close to home, presumably with other women in the same situation, confinement and control can be one consequence.

Human hunter-gatherers, for example the Gainj of highland Papua New Guinea, have an average of 43 months between births. Pennington (2001) calculated 39 months for hunter-gatherers, taking the mean of four non sedentary populations. Three and a half to four years between children seems normal for prehistoric people before the Neolithic, i.e. the adoption of agriculture, animal husbandry and a sedentary lifestyle.

How is this child spacing achieved? Mothers breastfeed their babies for at least the first two years of life, and unrestricted breastfeeding suppresses ovulation, preventing further pregnancies. How exactly this mechanism works is still under debate – and do not try this at home: it has been shown that in well-fed, western civilisations with a limited nursing culture breastfeeding alone is not a reliable method of birth control. The continuous, around-the-clock suckling of infants produces hormones in the mother that suppress ovulation, but the energy balance of a lactating woman may also have something to do with it (Thompson 2013).

https://motherhoodinprehistory.wordpress.com/2015/08/31/prehistoric-child-spacing/

No one suggested that we go back to hunting/gathering.