Pseudoarchaeologists often theorize that the ancient Egyptians couldn’t possibly have conceived and built the Pyramids. If pyramid building was introduced to the Egyptians by some other external influencer culture (aliens, Atlanteans, etc), there would be evidence of that cultural diffusion in the archaeological record. For example, if we assume that the island of Atlantis actually physically existed, and was home to a prominent “trading culture” (as many pseudoarchaeologists believe) there would be artifacts on many non-sunken land masses that would be stylistically identifiable to that specific culture. Further assuming that the Atlantean people travelled to ancient Egypt, there would be evidence of the intersection between the two cultures left behind in the material record – sunken ships, inscriptions in Atlantean language, bodies with different burial practices – that would be markedly different than the existing (well-studied and taxonomized) Egyptian cultures. In order for the hyperdiffusionist’s ideas to be true, there would need to be material remains (and accounts) of the outside culture within Egypt. These pieces of evidence would need to date back to the actual time of the Pyramids’ construction (not 10,000+ years ago).

Within the realm of actual science, Pyramids are a well-understood mortuary phenomenon. There is visible evidence of the architectural evolution from modest burial mounds to stepped pyramids to the capital-p Pyramids that we see today. There is no evidence, material or historical, that the idea for the construction and design of the Pyramids came from anywhere other than Egypt.

As for Atlantis, if it were anything more than a philosophical thought experiment, the island itself would have to be discovered. If there was a culture that existed on the island that diffused to other nations, there would be evidence in the material record of those interactions. For example, we would know that the Spaniards (and others) colonized the Americas almost regardless of historical documentation due to the overwhelming amounts of physical evidence that 1) multiple distinct cultures existed in that geographical space within the same time period, and 2) the cultures of the indigenous peoples experienced drastic changes during and after that time. No such evidence like this exists for “lost civilizations” like Atlantis or Lemuria or whoever. 

Iconic state level civilizations don’t pop up overnight and start to generate giant monuments that last thousands of years. They evolve and iterate until they become vast empires with skilled builders and established aesthetics. These iterations leave material remains that are able to be discovered and interpreted within scientific frameworks to come to conclusions.