At what point in human development can we recognise the presence of another person like us? It’s an age-old question which cannot be avoided, and I’ve been interested in the recent discussion about this on this blog. Each one of us comes to this question from a different perspective, so I would like to offer some reflections from the perspective of a baby doctor. As a neonatologist I have cared for many tiny and fragile babies, some as small as 22 weeks of gestation and weighing less than 500g. Continue reading
The Faraday Institute summer course is in full swing, and on Tuesday morning evolutionary biologist David Lahti presented some reflections about his own work on human behaviour. What he said was fascinating, and raises all sorts of questions regarding human personhood. The analogy that he used was the baking of bread. The ingredients he focused on were the ‘flour’ of genetics, the ‘water’ of the environment, the ‘yeast’ of agency and the heat of development. Not all of the ingredients are apparent in the finished product, but all are essential.
It would be easy to think that genetics is unimportant in the determination of behaviour. Over 90% of the prison population possesses a y chromosome, but being male is not considered a reasonable defence against criminal charges, and neither has anyone taken steps to prevent further violence by incarcerating all those in possession of such a chromosome (and perhaps that’s a good thing…)
Lahti spent the first part of his talk outlining some recent findings in the field of behavioural genetics, including alcoholism, trust, mate choice and political preferences. Amazingly (to me) there are indications of heritability for all of these traits, although because they are such broad categories it has proved difficult to find genes that play a major role in determining these characteristics. Continue reading
I’ve been blogging about astronomy recently. It’s an easy target really – anything that involves staring at the night sky is likely to move people to worship. But what about my own subject of biology? The living world is a lot messier, but it is just as amazing.
Our own development from sperm and egg to squalling baby takes just nine months. During that time, the instruction manual for a unique physical human being is read off from the DNA code that resides in every cell in our bodies.* It’s incredible that the information is all there in the 2 metres or so of code in each cell. DNA is about a billionth of a metre (2nm) wide, and is not visible with even the best light microscopes (these can only see things as small as about 50 nm). Inside the cell DNA is coiled up, in a number of complex stages, into a tiny mass that fits inside the nucleus of the cell.
Until recently I believed that we had enough DNA in our bodies to take us on an amazing journey. I was told that if all the DNA in each cell of your body – all 2m of it – was extracted and added end to end it would reach as far as the moon and back. That’s quite a thought.
But then I checked the numbers for a children’s talk that I was preparing and discovered that the story I had been told was way off the mark.
- We have about 50 trillion (50 x 1012) cells in our bodies.
- Multiply that by 2m, and you have about 100 trillion metres, or 100 billion (100 x 109) kilometres of DNA.
So yes, we do have enough DNA in our bodies to take us to the moon and back, but you can go much further than that – to the sun and back more than 300 times! I can’t even begin to comprehend that, but it’s very impressive. And I’ve ended writing about astronomy again…
I’ve been criticised for making the leap from ‘wow that’s amazing’ to belief in God. But that’s not what I’m doing. I don’t believe in God because of anything to do with science (see my earlier post for more on this). The point is that I believe in a big God, and learning more about how incredible the universe is helps me to understand a little more about just how big God is.*Except mature red blood cells or the lens in our eyes – in these cell types the DNA would get in the way so it’s broken down.