Heavier-than-air aircraft, yes. It is instructive to read actual contemporary arguments. Flighted birds seem to be limited in size well below human loading capacity; Helmholtz power-to-weight ratio calculations suggest that vultures are at about the size limit; birds are all muscle with very little relative carrying capacity; bird reflexes vastly outpace the reaction times available to a human operator; etc.
Please show us actual evidence from 1900 or earlier that human flight will be practical or even possible.
Birds are neither real evidence nor real at all[1].