They may be smaller than a pea, but make no mistake. The grey blobs of goo growing in Jürgen Knoblich’s laboratory in Vienna mark the beginning of something momentous, for these clumps of living tissue are nothing less than miniature human brains grown from genetically engineered skin cells.
These “cerebral organoids”, as Dr Knoblich described them this week, show the early hallmarks of human brain development, including self-organisation into distinct three-dimensional layers. They are roughly equivalent in complexity to the brain of a foetus at nine weeks’ gestation, he said.
Although the nerve cells in these organoids have begun to organise themselves in a similar way to real brain cells, they are still a long way from being able to generate the unique spark of consciousness that supposedly sets humans apart from other forms of sentient life.
There is something special about the human brain, which is why the idea of growing miniature brains in a laboratory raises ethical concerns about how far this work can or should be taken. Dr Knoblich acknowledged these anxieties but quickly dismissed the idea of “brain in a bottle” capable of conscious thought. “I do not think this is desirable and I do not think it will work,” he said.
But the fact is that we still know surprisingly little about the human brain other than it is the most complex structure in the known universe – yes, even cosmologists agree to that. And we certainly do not know how this three-pound bag of cells and chemical transmitters generates conscious self-awareness, or what some people might call “a soul”.
There are some 86 billion nerve cells in the brain and each of them make, and sometimes remake, elaborate connections between one another. Indeed, one estimate suggests there are more than 100 trillion nerve connections in the human brain. If all these connected nerves were to be unravelled and laid end to end, they could be wrapped twice around the Earth. But the brain’s complexity does not end there. Myriad chemical messengers, or neuro-transmitters, relay information across the gaps or synapses between the nerves. And for every nerve cell there are another 10 or 50 “support cells” in attendance, which play their own role in the intricate functioning of this most mysterious of human organs.
President Obama, in a speech at the White House earlier this year, targeted the brain with his own version of the Kennedy Moon speech. He has promised an initial $100m to map the activity of every neuron in the human brain in order to gain a better understanding of “how we think, learn and remember”.
The Obama brain initiative is not just about the inherent fascination we have with our own thinking machine. It is also about the practical and financial realities of coping with an ageing population and the growing burden of brain-related disorders, such as Alzheimer’s disease and other forms of dementia.
The loss of memory with age, for instance, is still a great mystery. How is it that we can sometimes still recall childhood memories in late life while every molecule in our brains has been replaced several times over? Why do some memories stay with us for long periods, while others disappear as fast as a set of car keys?
Solving the mysteries of the human brain will clearly be one of the biggest scientific projects of the 21st century. Modern brain scanners, such as functional magnetic resonance imaging, have brought unparalleled insights into the workings of the living brain – such as the realisation that London taxi drivers have bigger than average hippocampus regions to store the exceptional spatial memory needed for “the Knowledge”.
A century or more ago, studying the human brain was more or less limited to looking at what happens when things go wrong or missing. Perhaps the most notable example was the case of a 19th-century American railway worker named Phineas Gage who survived having part of his pre-frontal cortex removed in an accident with explosives and an iron tamping rod. Medical reports from the time suggest that Gage’s personality was changed beyond recognition. Before the accident he was mild mannered and civil. After it he became obstinate, argumentative and highly abusive – he was, as one report said, “no longer Gage”. It seems that the pre-frontal cortex of the human brain – the bit above our eyes – is really what sets us apart from other intelligent animals. In man, the pre-frontal cortex tripled in size in two million years of human evolution.
During our long prehistory, the human brain evolved to be significantly bigger and more complex in proportion to our body size than our nearest living relatives. It is three times larger than a chimp’s, for instance. Much of this evolutionary development took place within the cortex, the “higher” bit of the brain responsible for language, conscious planning and the control of the evolutionary older parts of the brain responsible for our basic instincts: aggression, feeding and sex.
But however much we may think we know about the brain, there is so much we do not understand. Scientists at the end of this century will no doubt look back and compare our current knowledge to the discredited 19th‑century idea of phrenology – reading a person’s mind by feeling the bumps on their head.
As things stand, human consciousness – our ability to analyse our thoughts and what other people are thinking – is probably one of the greatest mysteries in science. Evolutionists and physiologists are united in their ignorance of not being able to explain how consciousness comes about.
This is why Francis Crick, the co-discoverer of the DNA helix and one of the brightest intellects of 20th-century science, devoted his last years of life to understanding consciousness, which he compared to the scientific search for the soul. “What I want to know is exactly what is going on in my brain when I see something,” Crick said.
He died before he could find the answer. We are still a long way from knowing our own minds, but something tells me the blobs of grey matter living in Jürgen Knoblich’s lab may one day lead to the answer.