Final answer:
Von Daniken's Amorous Alien hypothesis lacks empirical evidence and is therefore considered unlikely. Astronomers would require solid physical evidence of extraterrestrial contact, and the nature of early Earth evidence makes it scarce. Scientific theories must be supported by evidence to be credible and maintained within the scientific community.
Step-by-step explanation:
Von Daniken's Amorous Alien hypothesis is considered unlikely primarily due to lack of empirical evidence. This hypothesis, which suggests extraterrestrial influence on human history, does not have the support of cultural anthropologists and is not substantiated by scientific methods. Theories about the past, and especially those involving extraterrestrial entities or events, require strong empirical support to be deemed credible by the scientific community. For astronomers to be convinced of an extraterrestrial spacecraft landing on Earth, they would need definitive physical evidence such as spacecraft remnants, signals, or observations that cannot be explained by current understanding of natural phenomena. The reason there is so little evidence of Earth's earliest history, including the period when life first began, is due to geological processes and the fact that early evidence is often lost or not preserved. Evidence-based approaches in science, including the scientific method and peer-reviewed research, are key to establishing or discarding theories.
Contradictory observations or a lack of supporting evidence can lead to the discarding of scientific theories. Linguistic theories and hypotheses also require substantial evidence, which can be hampered by the immense diversity of languages and the complexity of linguistic evolution. Moreover, the Linguistic Society of Paris's historical ban on debates about the origin of language reflects the difficulty in studying topics with insufficient empirical evidence. This intersects with the study of the natural origin of life on Earth, where several competing hypotheses exist, each backed by its own set of evidence, illustrating the vital role evidence plays in shaping scientific discourse.