When does consciousness develop in human beings?

Consciousness, like 'life' is not an on/off thing. We get this image of the on/off thing from noticing that death seems to switch it off, permanently, and it cannot be revived. But that does not mean that either consciousness or life *developed* suddenly. It only means that current living organisms need a constant flow of energy to *maintain* consciousness, so that flow can't be interrupted.

So it is impossible to pinpoint a moment in development (either in evolution, or in development of an individual human being) where consciousness starts. It more correctly *emerges* as a gradual process. Neither a sperm nor an egg cell are any more "conscious" than any other cell in your body. Likewise a fertilized egg cell (fusion of egg and sperm) ... it is no more "conscious" than a skin cell or a nerve cell. Over the course of gestation the brain develops the structures needed to support consciousness, but it is an ongoing process. It is even hard to say whether a newborn human baby is even fully conscious. We have no way to measure consciousness except by way of interracting with it ... which can't happen until a baby is able to start communicating beyond instinctual cries.

So there is never a 'poof'. Not as far as we can test.

This is a question that is loaded with difficulty. Human consciousness does not just snap on, nor is it present in a fertilised egg cell. Instead consciousness of environment develops slowly from about 3 months after conception. When it is fully developed is also a difficult topic, some people may say at an age of around 1 yr old when a child becomes properly aware of their sevlves as an individual.

Hope this helps

Martin