Australians have access to some of the best healthcare in the world, allowing us to avoid many preventable illnesses, receive good care when we’re unwell and live longer. Ironically, this advantage may be fuelling an epidemic of obesity, diabetes and, according to new research, cancer.
The University of Adelaide study found that the world’s wealthiest countries have much higher rates of cancer than much poorer countries.
Looking at cancer rates over four to five generations, comparative anatomy and human evolution expert Professor Maciej Henneberg and PhD student Wenpeng You, analysed global cancer data from the World Health Organisation from 173 countries.
Although treatments have improved, cancer rates have not and worldwide, cancer is now the second leading cause of death after cardiovascular disease. The researchers found that some cancers had quadrupled in the past 100 years and, across the board, incidence was higher in the top 10 countries; countries with low mortality (and fertility) rates, access to quality healthcare and socioeconomic status.
In fact, in the “top 10” testicular cancer was 14 times more common, lung cancer 12 times more common, melanoma was 10 times more common and brain, breast and pancreatic cancers at least three times more common.
These countries included Iceland, Singapore, Japan, Switzerland, Sweden, Luxembourg, Germany, Italy, Cyprus and Andorra, while the “bottom 10” countries included Burkina Faso, Chad, Central African Republic, Afghanistan, Somalia, Sierra Leone, Democratic Republic of the Congo, Guinea-Bissau, Burundi and Cameroon.
Henneberg and You argue that advances in medical science have replaced natural selection; in the “top” countries, more people survive illnesses that naturally they wouldn’t and pass on genetic mutations to their children resulting in increasing predisposition to cancer (and, as Henneberg’s previous research has shown, obesity and diabetes).
“I realise that our paper may be seen as controversial,” says Henneberg, head of the University’s biological anthropology and comparative anatomy research unit.
But, he adds, this study is the latest in a line of research over the course of 20 years exploring “declining opportunity for natural selection in modern populations”.
“It is a piece in the series of research topics showing that reduction of the opportunity for natural selection through undoubtedly beneficial medical interventions produces side-effects that need to be attended to before they become serious,” Henneberg says.
While most of the cancers that are only “partly heritable”, meaning that genetics may elevate risk but don’t make it inevitable, Henneberg says that mechanisms that repair cancer-causing mutations (which can result from multiple causes including radiation, viruses and tobacco smoke) and susceptibility to mutations depend on the inherited genetic material.
“In short – cancers are not heritable, but a tendency to be susceptible to cancer is,” he says.
While natural selection may result in fewer people without or with less cancer genetic background in countries that are “worse off”, the answer to the problem is complicated.
“The old approach of preventing people with genetic faults caused by mutations from having offspring – eugenics – is entirely unacceptable ethically and morally repulsive,” Henneberg says.
“Therefore we must resort to repairing genes damaged by mutations – to invest more in research on gene repair. This is a very difficult research also fraught with ethical problems of ‘designer babies’. Because of difficulties we tend to sweep this whole area under the carpet while incidence of various faults – not just cancer but also colour blindness, diabetes and metabolic faults related to food processing in the body – is increasing in human populations burdening afflicted individuals and health systems.”
Henneberg predicts the future solution like in the ability of medical science to develop better methods of treatment, “including blocking actions of defective genes”.
“We accept technological intervention into tissues of our bodies, we accept chemical interventions into workings of our bodies every time we take a pill or injection, what is the difference when it comes to adjusting operation of genes?”