Humans have almost always been overpopulated.
Populations grow and shrink exponentially when there is a difference between the birth rate and the death rate. If the birth rate is below the death rate the species goes extinct. Birth rates do not magically match death rates, thus every species that is not extinct has a birth rate above their death rate, until their numbers reach the limits of what can be maintained by the environment. Death rates are forced to rise to at least match the birth rate in order to stop the population growth.
Humans are no different. We have not throttled our birth rates, and have been in existence for enough time to have hit the limit.
This means that humans are overpopulated, and have generally always suffered the effects of overpopulation.
We can explain that fact that our numbers have grown, and stabilized, and grown, and stabilized throughout history by the fact that we have the ability to discover better techniques for acquiring our sustenance. When we discovered farming techniques, we raised the limit, and the population bloomed to fill it back up. When we discovered how to make fertilizer, we raised the limit, and the population is again blooming to fill it back up.
We must not assume we are not overpopulated. We must assume we are overpopulated.