OUT-OF-PLACE ARTIFACTS

A Singer sewing machine has been found in one of the oldest strata of an archaeological site of Alcalá de los Gazules (Spain). This turns everything we knew about prehistory upside down. Until now we believed that men of twenty thousand years ago used bone and ivory needles to tie together animal furs. Now we know that, in parallel, there were seamstresses who used sewing machines and who knows if instead of fur dresses they made sophisticated evening gowns. What does this reveal to us? Indeed, this discovery reveals that, in prehistory, humans had contact with aliens. Now, don’t jump to conclusions. Nobody hints that Mr. Isaac M. Singer was extraterrestrial. That would be absurd. There are many other more plausible explanations. For example, it’s possible that in the late 19th century Mr. Singer sold a batch of his sewing machines to an extraterrestrial civilization and that then this civilization sent an alien expedition back in time carrying with them a Singer sewing machine as a gift to prehistoric humans to whom they taught how to make tailored suits. 
I shall never tire of repeating that the researcher must always tend towards the simplest explanation of all possible ones, discarding the most elaborate ones as highly improbable.