Did change in the earth’s orbit cause humans?
The fundamental question in human evolution is what ‘caused’ such a phenomenal species as ourselves to emerge and evolve? Theories are often competitive, but this can be misleading as scale and intermediate mechanisms are important. For example, it is often said that culture, language and intelligence are what is unique in humans, and needs explaining. The explanation is clearly related to our especially large and complex brains. But we can ask what ‘causes’ large brains to evolve, and it has been argued that large brains relate to large social groups. So ‘large social groups explain human evolution (sometimes called the social brain hypothesis). But we can equally ask why do some primates live in larger socials groups? The explanation now is about the availability and distribution of resources (behavioural ecology models), but this in turn leads to questions about the causes of the distribution of habitats and the role of climate. So the final question might be, what determines climate change, and the answer is variation in the earths orbit around the sun – so humans are ‘caused’ by astronomical events!
Obviously this is not an interesting answer, but reminds us of the importance of finding the right level of explanation and causality, and to consider how they fit together.