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The live online debate with Susan Greenfield was held on Sunday, February 14.

Here is a transcript of that debate, based upon the article below.

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By 2050 humanity could have been left behind. Scientists predict that by then we will be creating a new species, genetically enhanced and ready to grasp immortality.

Is this what we want?

By Susan Greenfield

BY THE END of the 21st century, if not sooner, some scientists assure us, we will have the technological know-how to postpone death indefinitely.

We will spend most of our prolonged lives in the bloom of youth. Cancer will be a thing of the past.

We will be able to cure countless other illnesses with the help of cloned organs. We will be creating designer animals, maybe even designer babies.

We will be using chemical dexterity to alter our emotions, and implants to boost our brain power. We will be so different from what we are today that we might decide we no longer even belong to the same species.

The days of Homo sapiens are numbered. The future belongs to Homo superior. But there is one important question that we have not even asked yet.

Will Homo superior, as currently advertised, really be superior, and if so, what does superior really mean?

There are some things we tend to argue about less than others, and one of them is the importance of good health.

Will health and "superiority", then, go together?

We can be almost absolutely certain that many more of us will be enjoying good health in the next century. Genetic screening and gene therapy will have eliminated many of our worst scourges.

No more cystic fibrosis or Huntington's chorea. Neither will it be simply a case of having constrained Nature.

We will also have Nurture under our technological thumb. It's not too difficult to imagine a future in which we are all fed a personalised computer-calculated diet, exercise at the dictates of interactive-silicon personal training multimedia, and accept spare-part surgery as routine.

BUT WHAT ABOUT the ultimate non-material commodity; a better mind?

It has become fashionable to claim that this, too, is about to become a reality. Some point to recent advances in molecular biology and say that it is only a matter of time before we have the wherewithal to suppress the gene "for" shyness, or introduce the gene "for" intelligence.

Once we have fully mapped the human genome, once we know what every gene in the human body expresses, then surely it will be scientific child's play to tweak a few strands of DNA to fine-tune our brains.

But what the people who make these claims do not seem to realise is that the brain is not merely a genetic potpourri. The human body contains about 1m genes.

This sounds enormous, until you take in the fact that the human brain has 100billion brain cells. And that number is as nothing compared to the number of synapses, or connections.

There are 1,000 to 100,000 synapses for every brain cell, bringing us to a total of about 100,000,000,000,000! It is unlikely that genes dictate the formation, distribution and functioning of each of these individual connections, but even if we assume that they dictate 1m of them, we are still left with a billion-fold discrepancy.

So what does determine the configuration of these other circuits?

The answer is: real life; recent studies have shown that synapses are forged, strengthened or suppressed by personal experience.

The biggest problem lies in what we perceive genes to be "for". It would be wrong to point to the gene "for", say, criminality.

All a single gene can do is express a tiny chemical. It does not contain a sophisticated behaviour pattern trapped in the structure of DNA.

True, the chemical will aid and abet the functioning of certain brain cells in certain circuits, which in turn are nested in ever more complex brain hierarchies, which eventually add up to a complete brain structure.

But these brain structures are not independent mini-brains. There are no "centres for" love of children or patriotism. Just as a single brain function such as memory is distributed among many different brain regions, so, too, can a single brain region be involved in many different functions.

It is unlikely that gene tinkering will allow for the clean targeting of faults and virtues.

It is far more likely that we will be setting in train processes and phenomena over which we do not have total control and where outcomes cannot always be predicted.

And even if we leave the genetic minefield, we might still end up in Brave New World. Running alongside all this discussion of genes "for" shyness or criminality is a lot of talk about chemicals that will allow all of us to give our work and our lives 110%.

To be that bit cleverer, that bit bolder. To be, in a word, superior. Drugs, however, are blunt instruments: when they modify brain chemistry, they modify it everywhere.

The effects are always indirect, and work at the level of single cells. The idea that there is a drug, and hence a specialist chemical, for something as complex as memory is, therefore, completely misleading.

WILL BRAIN IMPLANTS be able to refresh the places chemists and gene manipulators cannot reach?

Just pop in a few silicon memory chips and have instant access to superior knowledge?

Alas, there is no discrete little cerebral island responsible for French or the names and dates of the Plantagenets. And, in any case, the whole point about the human brain is not that it can store facts, it's what it can do with those facts, and how it can generate ideas.

There may be those who fantasise about achieving mental immortality by exchanging our messy biological brain tissue for silicon.

But to create a technobrain that was as good as a human brain, you'd have to make sure it had the same single-cell structure, the same number of synapses, the same three-dimensional circuitry, the identical macro-level chemical organisation, the same restless orchestrations of brain regions, and the same intimate electro-chemical dialogues with the rest of the body.

In other words, you'd have to know how your mind is different from my mind, and why and how the imagination works, and what creates creativity.

You would have to know what consciousness is, and what a "self" is, not just metaphysically, but in physical, brain terms. These are the ultimate goals of science. And until we can achieve them, we cannot claim that we have it in our sights to create a better mind.

And even if we do manage to create a race that is demonstrably superior to Homo sapiens in other ways - because it lives longer, smiles more often, and can go shopping without a calculator.

There remains a final question: what is Homo superior for?

My version of Homo superior would be a little less interested in "mastering" nature, or changing the way individual minds work, and more interested in understanding and celebrating ourselves that bit more.

To be Homo sui generis.

Professor Greenfield is Director of the Royal Institution of Great Britain

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