The human brain is, by some accounts, the most complex and powerful object in the known universe. The product of billions of years of evolution, it is an advanced network of neurons, neurotransmitters, and other biological matter. It enables us to understand the universe and perform the complex tasks through which humanity has come to dominate the planet.

Someday, it may become possible to “upload” the content of our biological brains into electronic computers, just as we now upload attachments to emails. Your uploaded, computerized brain would—if all goes well—process information just as your biological brain does now. It would have all your memories, your ideas, and your ways of thinking. It would, in a sense, be “you”.

If we upload our brains, what would happen next? This is the theme of a new book The Age of Em: Work, Love, and Life When Robots Rule the Earth by Robin Hanson , an economist at George Mason University. The book provides vivid descriptions of the world of uploads, or “ems,” which is short for brain emulations. It covers a wide range of details, from the size of their cities to the types of music they might listen to.

For two reasons, uploaded ems might become very powerful. First, they may be able to think a lot faster than biological humans by running on faster hardware. Second, it might be possible to copy them repeatedly, just as we now copy ordinary digital files. If both of these conditions hold, then even a single uploaded brain could turn into a vast population of hyperfast thinkers. Humanity is unlikely to be able to keep up.

The Age of Em describes a world in which uploads dominate the global economy. Some biological humans carry on at the margins of the new upload society, living on income from investments in upload corporations, and everyone else dies out. But that seems too optimistic: the hypersmart uploads should figure out a way to take all the income from the biological humans. Unless they graciously give us biologicals some sort of welfare to live on, we would go extinct.

This begs the question: Should we even be uploading our brains in the first place? Again, The Age of Em is optimistic. It sees uploads as being smarter, more rational, and generally more successful than biological humans, making them a worthy replacement. That may well be true, but we can hardly take it for granted. There are several reasons why we should be extremely cautious about uploading.

A key issue is whether the uploads would be conscious. Consciousness is what brings our lives all the emotions and experiences that make life so worth living. If uploads are conscious too, then they might fill the world with the same beautiful emotions and experiences that biological humans have. Or, due to differences in their mental hardware, they might have different emotions and experiences—and there’s no guarantee those emotions would be as positive as ours. However, the biggest risk is that they might not be conscious at all. If biological humans are replaced with unconscious, emotionless uploads, then the most beautiful aspect of humanity could be lost forever.

There is reason to believe that uploaded brains would be conscious. Some theories of consciousness propose that it emerges from the interactions of different parts of our brains. If computerized brains have the same sorts of interactions, then perhaps they would be conscious too. But the science of consciousness is far from settled. Indeed, it is hard to know for sure what is or isn’t conscious. The chance that uploads would not be conscious is a reason not to upload our brains in the first place.

Another issue is how well the uploads would manage the planet. Currently, biological humans are struggling to handle a range of threats from global warming to nuclear weapons. These threats risk getting out of hand, destroying our global civilization forever. If uploads were more successful at addressing these threats, that would be a big point in their favor.

Perhaps uploads would do a better job. Their fast brains might figure out solutions to the risks before things get out of hand. However, uploads could also create new risks. For example, The Age of Em proposes that uploads might all live in a few giant megacities. That would make them extremely vulnerable in war. Just a few big bombs could knock out the entire population. This new risk could outweigh the uploads’ ability to address existing risks, but the calculus is murky.

Fortunately, we don’t have to make the decision just yet. The technology for uploading is a ways away—probably several decades or centuries or maybe even longer. That gives us some time to sort out these thorny issues.

A decision we face right now is whether to speed up or slow down research in precursor fields of science and technology such as neuroscience and imaging technology. These are the fields that need to advance in order for uploading to become possible. Given how murky the uploading risk-benefit calculus is, a case can be made for holding off on this research until we better understand whether uploading is a good idea.

However, these fields have a lot of other applications, most of which are good for the world. For example, neuroscience research advances medicine and artificial intelligence. Imaging technology has a range of applications including medicine, pollution monitoring, and even landmine detection. Are these benefits worth the risks of uploading? That’s hard to say. In the near-term, the benefits probably outweigh the risks, but there may eventually be some lines of science and technology should be restricted.

What is clear is that the prospect of uploading warrants serious attention now. If we wait until the technology is already available, it could be too late to figure out what to do with it. Uploading could cause humanity to lose control of the world or even go extinct. It is never too early to figure out how to get it right.