Professor Mark Thomas is an evolutionary geneticist at University College London, specialising in how changes in our DNA allowed us to adapt to changes in our lifestyle over the last 10,000 years. Among those changes, the mutations that allow us to continue to drink milk into adulthood are arguably the most advantageous characteristic Europeans have evolved since then. There was no going back to our hunter gathering ways after that.
The differential survival rates of those who could and could not digest the sugar in milk (lactose) are evident from the number of people who now carry that mutation (LCT -13,910*T). In the language of evolutionary biologists, this is called strong selection pressure. Unlike plants and their fruits, which are often toxic, and prey animals with their legs, teeth and claws, milk is the only food that evolved specifically to be nutritious (for calves in this case, but close enough for us) and can be made available year round. Raw milk was relatively safe to drink, even before modern pasteurisation, which kills any contaminants like brucellosis, E. coli, salmonella and miscarriage-causing listeria. Drinking milk back then was a life or death factor in the positive sense.
Cattle were domesticated around 10,500 years ago, not long after the beginning of the farming age – about 12,000 years ago when the ice age had ended – whereas the random mutation for lactose tolerance happened in the last ~7500 years. In the 3000-year interim there was nothing to stop people consuming yoghurt, which the milk quickly turned to in the warm temperatures of the near East, and butter and cheese, which contain almost no lactose. Milkable animals were already valuable portable food supplies.
Farming arrived in Britain around 6100 years ago, Mark tells me. The farmers who took this new knowledge west from its origins in Anatolia – along with their entourage of cattle, pigs, sheep, goats and dogs – occasionally interbred along the way with Hunter Gatherers, a strapping breed of men and women with mostly dark skin, straight dark hair, and blue eyes. Mark shows me a picture of one inferred from archaeological remains and DNA. It is no surprise then that the savvy, though less statuesque, farmers wanted to interbreed with this attractive people. The successful farmers gradually absorbed or outbred the Hunter Gatherers, just as the technologically superior breed of humans coming out of Africa had outcompeted Neanderthals 60-40,000 years ago, occasionally mating with them and thus absorbing some of their genes. We all have about 2.5% of Neanderthal DNA unless we are African in ancestry – they never had the pleasure of meeting their distant relatives who stemmed from a previous African exodus a few hundred thousand years earlier.
When the farmers arrived in Britain, they would have encountered sparse bands of Hunter Gatherers. Another big influx of agriculturalists came to Britain from the Ukraine 4000 thousand years ago, adding new genetic material to the mix. Mark cannot say what prompted this significant migration – it could have been climate change, or improved weapons, or some other factor. They don’t know.
Fast forward 4000 years to 2016.
Milk is still the most complete food in liquid form – the holy grail of modern day convenience marketers – and in the UK and New Zealand is now cheaper than petrol and water,*especially French water with gas in it. While profits soar for purveyors of bottled water – including vast quantities tapped from New Zealand’s pure reserves and gifted to international marketers for peanuts – we are giving milk away for below production cost, and way below the cost to the environment. Bottled water is bought mainly by people in countries where the tap water is safe to drink. The carbon cost of a bottle of water is reportedly 1000 times that of a glass from the tap. The multiplicity of water brands – all containing water of indistinguishable quality – are ranged alongside the veritable wall of flavoured, gassy and often caffeine-loaded sugared waters, which are also oft times cheaper than plain water, though they cost the country millions in healthcare.
Setting aside for the moment all our worries about water pollution and supply, methane emissions and the ethics of industrial farming, New Zealand makes milk better than any other country. More efficiently, cheaply, and with the lowest carbon emissions. And if we don’t have too many cows, we can feed them all on grass without supplementary imported palm oil kernel. But right now, there is too much milk for the world’s diverse and fickle beverage appetites. We’d be better off selling our own water with added value carbon dioxide or the memory of a nano-nothing of a homeopathic “remedy”. Perhaps Fonterra could invert its operation by exporting the water they painstakingly squeeze out of the milk to make powder – actually a tiny fraction of what went into it the first place. Water from a cow may not be a winning sales proposition but with a French label, it might work – eau de vache?
Although pretension to lactose intolerance seems to be fashionably retro in certain educated suburbs, it is actually quite rare among the people of predominantly Northern European heritage who inhabit those suburbs. No pre-modern human ever boasted about lactose intolerance – probably because they were dead from it. Ireland has the highest incidence of lactose tolerance, closely followed by Scotland, England and southern Sweden. The selection pressure could have been greater because the Vitamin D and calcium milk contains were more necessary to northern folk. Anyone who has been to Scotland or Scandinavia would understand that a daily dose of sunlight is hard to achieve.
Unfortunately, many in these populations, including our own, are not exploiting their natural advantage, preferring sugared water to milk, with more serious consequences than insufficient Vitamin D and calcium. Sadly, obese people – perhaps victims of genes geared to expect a different food environment – are less fertile so this could be an evolutionary self correction.
Milk, and farming technologies more generally, have saved more lives, or allowed more lives to be than any other development. Sure, we are beginning to seriously regret those billions of other lives allowed to be as the planet overheats, with agriculture continuing to make a major contribution.
Mark reels off these stats on the top science and technological life-savers and –makers:
- Fritz Haber and Carl Bosch (nitrogen fixing process that yields artificial fertiliser) – 2.7billion lives
- Norman Borlaug (I’d never heard of him, have you?) An Iowa farmer who developed semi-dwarf, high-yield, disease-resistant wheat varieties – 1 billion lives
- Karl Landsteiner (blood groups) and Richard Lewisohn (blood transfusions) – 1 billion lives
- Edward Jenner (Smallpox Vaccination ) – 500 million lives
So that’s c5.2 billion – more than the number of people born since 1900.
I have mixed feelings about that thought as I heave my suitcase up the steps to the Circle Line Tube Station through the madding crowd. Then, another “otherwise would not have been” comes alongside me and without a word carries my bag up the next staircase. My world view is transformed.
* depending on the size of milk or water bottle) (http://www.independent.co.uk/news/uk/home-news/how-did-milk-become-cheaper-than-water-9990760.html). The prices of milk, water and soft drinks vary depending on brand and size of bottle.
My grateful thanks to Mark Thomas
