by Tom Standage
Early attempts to produce a synthetic gene drive focused on enzymes called homing endonucleases. These can insert copies of the genes that encode them into chromosomes, thus increasing both their number and the likelihood that they will be passed on to the organism’s progeny. Engineering these to do humanity’s bidding (by disrupting fertility genes, for example) proved difficult. That problem was solved in 2015, though, when Valentino Gantz and Ethan Bier of the University of California, San Diego, used CRISPR-Cas9, a recently discovered gene-editing tool, to make a gene drive that could be inserted anywhere in the genome of a fruit fly.
The ease with which gene drives can be made with CRISPR-Cas9 has, however, provoked fresh worries about the technique, which would have to be addressed before gene-drive-carrying organisms could be let loose in the wild. First, a gene drive that somehow hopped from a target species into the genomes of other animals might wipe them out before anything could be done about it. Researchers are therefore developing ways to switch off gene drives. Second, some ecologists worry about the side-effects of exterminating entire species. Kill off malaria-carrying mosquitoes, for example, and animals that feed on them and their larvae will also suffer. Third, it is doubtful that all countries would agree to organisms harbouring gene drives being deployed on their soil. So there would need to be some means of confining the drive’s effects to a particular area. Initial trials of the technology are likely to be run on small, uninhabited islands. Finally, a study published in 2017 in the journal PLOS Genetics added to the evidence that gene drives simply may not work. Just as insects and pathogens evolve resistance to new pesticides and antibiotics, so gene drives, too, may provoke resistance. They may do so far faster than many suspect.
None of this means that gene drives will not eventually fulfil their promise. Researchers continue to work on drives intended to eliminate malaria and mosquitoes, and to create mice that cannot bear daughters, to wipe out invasive rodents. Others are trying to create white-footed mice that would be immune to infection by the bacteria that cause Lyme disease. That would prevent the ticks that eventually transmit the disease to people from becoming infected when they feed on the mice. Gene drives are also expected to play a role in the government of New Zealand’s plan to rid that country of all rats, stoats and possums by 2050. Nonetheless, the study in PLOS Genetics strengthens the case that tricking evolution will be hard. To paraphrase Jurassic Park, life finds a way.
Why it is so hard to fix India’s sanitation problems
India vies with China to be the world’s fastest-growing large economy, but its record on basic sanitation is dreadful. Around 450m people relieve themselves in playgrounds, behind trees, by roadsides, and on railway tracks and river banks. In cities, 157m urban dwellers, more than the population of Russia, lack decent toilet facilities. Much of the solid waste is emptied into rivers, lakes and ponds untreated. The World Bank says one in ten deaths in India is linked to poor sanitation. From contaminated groundwater, children pick up chronic infections that impair their bodies’ ability to absorb nutrients. Almost 44m children under five, says the bank, have stunted growth, and every year more than 300,000 die from diarrheal diseases. What can India do to change this grim reality?
In 2014 the government pledged to end open defecation by 2019. That year marks the 150th anniversary of the birth of Mahatma Gandhi, who considered sanitation to be sacred and “more important than political freedom”. Authorities have set aside $29bn for the nationwide programme, which claims to have constructed 49m household toilets to date, with another 61m still to go. Families get 12,000 rupees ($187) to build a toilet. The initiative is part of a long line of schemes that go back to the country’s first five-year plan of the early 1950s. The Indian government has been subsidising lavatories in remote villages for over three decades. Between 1986 and 1999 it installed 9.4m latrines, giving 7.4m more people access to sanitation every year. But improved coverage does not guarantee greater usage. A survey by the Research Institute for Compassionate Economics in 2014 found that in 40% of households with a working toilet, at least one family member preferred to defecate outside.
People in villages often fail to acknowledge that a lack of sanitation is a problem. Many use toilets only in emergencies, worrying that the cesspits will clog up quickly when, in fact, they are meant to last a family of five about ten years. Caste division plays a part, too. Villagers are reluctant to empty latrine pits manually, a task relegated historically to dalits (formerly untouchables). Some consider defecating in the open to be a sign of virility, and believe a stroll to the fields aids digestion. Toilets, often the only concrete structure in a house, may end up being used to store firewood, grass, chickens, cow-dung cakes and food grains, or double up as goat-sheds. Implementation of the scheme is patchy, too. Families who receive a toilet-building subsidy do not always build one. Often the sarpanch (village head), the junior engineer who surveys the site and the local contractor are in cahoots and skimp on building materials and design, says Nitya Jacob, a sanitation consultant.
Simply punching holes in the ground at breakneck speed will not solve the problem. India could learn from neighbouring Bangladesh, which reduced the prevalence of open defecation from 34% to 1% between 1990 and 2015. As part of a sustained effort, its government partnered with village councils to educate people in the merits of good sanitation. Instead of just highlighting the hazards of open defecation, it extolled the virtues of clean sanitation. Having a toilet became a symbol of dignity. Women decided on the location and type of toilets to be built in their homes. In India, by contrast, officials have at times brutally punished those who defecate outside, either by having them beaten up, or denying them government benefits like pensions and monthly household provisions unless they build a toilet at home. In the short term such coercive tactics might work to increase the number of installed toilets. But they will do little to promote their use.
Why some deadly diseases are hard to eradicate
Bubonic plague brought terror to medieval Europe. Over a third of its population perished from the “Black Death” in the 14th century, hastening the end of the feudal system. As a bacterial disease, the plague these days is generally treatable with modern antibiotics. Nonetheless, it persists beyond the grim annals of history. In June 2017 health authorities in New Mexico, in the south-western United States, announced that three people had been diagnosed with the disease in the previous month alone. This is a marked uptick for a country that records around seven cases a year nationwide, according to the US Centres for Disease Control and Prevention.
The plague
Source: WHO
Zoonotic diseases such as the plague, Ebola and avian flu – which are generally carried by animals – are extremely hard to eradicate. The plague is caused by a bacterium, Yersinia pestis, which infects fleas, which in turn live mainly on rodents. In Europe, those fleas lived mostly on black rats. In America’s south-west, the site of most cases observed in the rich world, the fleas have shifted to rural squirrels and prairie dogs. No vaccine has been developed for the plague, and if the illness is not treated quickly with drugs the death rate is high. The most common form is the bubonic plague, which is spread by flea bites or by contact with animals, and which kills 30–60% of those infected. A rarer pneumonic form, which spreads to the lungs and can be transmitted by sneezing or coughing, is invariably fatal without treatment. In America four people died of the plague in 2015, its highest annual toll for 30 years.
Worldwide, however, the plague is mainly a disease of poverty. Natural focuses – areas in which the bacteria, fleas and animal reservoirs might create the right conditions for the plague to spread – are found in much of the world. But most cases occur in countries where people live in unsanitary conditions, and where treatment may be slower. Between 2010 and 2015 there were 3,248 cases and 584 deaths. The worst-affected country is Madagascar: three-quarters of all new infections and deaths occur there. And the disease is springing up in new places on the island. In Ja
nuary 2017 the World Health Organisation (WHO) confirmed that 62 cases, including 26 deaths, had been reported in districts of Madagascar that had not seen an outbreak since 1950. The ancient killer may be less deadly than in the past. But it has not gone away.
Why China is sick of foreign waste
China is the world’s biggest consumer of raw materials. Each year it buys billions of tonnes of crude oil, coal and iron ore. But there is one commodity market in which the country may soon play a less dominant role: waste. In July 2017 China told the World Trade Organisation that by the end of the year it would no longer accept imports of 24 categories of solid waste, as part of a government campaign against “foreign garbage”. Government officials said restricting such imports would protect the environment and improve public health. But the ban affected billions of dollars in trade and put many Chinese recyclers out of business. Why was Beijing so eager to trash its trade in rubbish?
For decades China had been a major processing centre for the world’s recycled waste. In 2016 the country imported 45m tonnes of scrap metal, waste paper and plastic, together worth over $18bn. Paying foreign firms for trash may have seemed like an unfair deal, but the trade benefited both sides. Exporters earned a return on their leftover waste, much of which might otherwise have ended up in a landfill. Chinese firms, meanwhile, gained access to a steady supply of recycled materials, which were often cheaper and less energy-intensive than domestically sourced raw materials – recycled steel, for example, requires 60% less energy than steel produced from iron ore.
Such economic benefits came with costs, however. Imports of recyclable waste were often dirty, poorly sorted or contaminated with hazardous substances. Even when such waste was safely imported, it was not always recycled properly. In 2002 Chinese authorities faced widespread criticism after a documentary showed workers in Guangdong province crudely dismantling discarded electronic devices and dumping the toxic remains into a river. A more recent film, Plastic China, examined the environmental damage caused by the country’s plastic-recycling industry, which is dominated by thousands of small-scale outfits that often lack proper pollution controls. Facing growing public pressure, Chinese authorities began cracking down. In 2013 the government launched “Operation Green Fence”, a campaign to block imports of illegal and low-quality waste through improved inspections of container ships. In February 2017 Chinese customs officials announced “National Sword”, an initiative aimed at reducing illegal shipments of industrial and electronic waste. The ban on foreign garbage is another example of such efforts to clean up the industry.
The government says the ban will protect the environment. But analysts point out that most of the waste consumed by China’s recycling industry comes from domestic sources, not imports. Waste has piled up in Western countries as exporters looked for alternative buyers in Malaysia, Vietnam or Indonesia. What cannot be sold will probably end up in a landfill.
Why are wolves coming back in France?
Residents of Lozère, a hilly department in southern France, recite complaints that can be heard in many rural corners of Europe. In remote hamlets and villages, with names such as Le Bacon and Le Bacon Vieux, mayors grumble about a lack of local schools, jobs, or phone and internet connections. Farmers of grazing animals add another, less familiar concern: the return of wolves. Eradicated from France in the 20th century, the predators are gradually creeping back to more forests and hillsides. “The wolf must be taken in hand,” said an aspiring parliamentarian, Francis Palombi, when pressed by voters in an election campaign in 2017. Tourists enjoy visiting a wolf park in Lozère, but farmers fret over their livestock and their livelihoods. An official estimate suggests that France was home to some 360 wolves in 2017, up from roughly 300 in 2016. The number of packs increased from 35 to 42. Wolves have been spotted in dozens of departments in France in recent years; there was even a report of a wolf pack encircling a lone walker. Why are they back?
As early as the 9th century AD, the royal office of the Luparii – wolf-catchers – was created in France to tackle the predators. Those official hunters (and others) completed their job in the 1930s, when the last wolf disappeared from the mainland. Active hunting and improved technology such as rifles in the 19th century, plus the use of poisons, caused the population to collapse. But in the early 1990s the animals reappeared. They crossed the Alps from Italy, upsetting sheep farmers on the French side of the border. Wolves have since spread to areas such as Lozère, delighting environmentalists, who see the predators’ presence as a sign of wider ecological health. Farmers, who say the wolves cause the deaths of thousands of sheep and other grazing animals, are less cheerful. They grumble that green activists and politically correct urban types have allowed the return of an old enemy.
Several factors explain the changes of the past few decades. Rural depopulation is part of the story. In Lozère, for example, farming and mining supported a population of over 140,000 residents in the mid-19th century. Today the department has fewer than 80,000 people, many in its towns. As humans withdraw, forests are expanding. In France, between 1990 and 2015, forest cover increased by an average of 102,000 hectares each year, as more fields were given over to trees. Now nearly one-third of mainland France is covered by woodland of some sort. As habitats for wolves have grown, the number of hunters has fallen. In the mid-to-late 20th century over 2m hunters regularly spent winter weekends tramping in woodland, seeking boars, birds and other prey. Today the Fédération Nationale des Chasseurs, the national hunting body, says only 1.1m people hold hunting licences, though the number of active hunters is probably lower. The protected status of wolves in Europe – hunting them is now forbidden, other than when occasional culls are sanctioned by the state – plus the efforts of NGOs to track and count the animals, have also contributed to the recovery of wolf populations.
As the lupine population of Europe spreads westwards, with occasional reports of wolves seen closer to urban areas, expect to hear of more clashes between farmers and those who celebrate the predators’ return. Farmers’ losses are real, but are not the only economic story. Tourist attractions, such as parks where wolves are kept and the animals’ spread is discussed, also generate income and jobs in rural areas. The future of more isolated departments, such as Lozère, probably depends as much on luring tourists as on the success of farmers. The wolf can be an ally, not only a threat.
Why biggest isn’t fastest in the animal kingdom
For 30 years viewers of the Discovery Channel have eagerly tuned in to Shark Week, an annual block of programming intended to promote understanding and conservation of the razor-toothed denizens of the deep. Although regular audiences have learned plenty about how sharks live in the wild, it had never been demonstrated that sharks can actually swim faster than humans. But in July 2017, to kick off that year’s Shark Week, the channel staged the first-ever race between mankind’s speediest swimmer and a great white shark. Although Michael Phelps has won 23 Olympic gold medals, the shark proved to be a tough opponent: it beat his time over 100 metres (328 feet) in open water by two full seconds, 36.1 to 38.1. In humanity’s defence, the race was not held under usual conditions: for safety reasons, and to ensure the competitors did not distract one another, they raced separately rather than being in the water at the same time.
Man v beast
Body mass and maximum speed of species, by movement type
Source: “A general scaling law reveals why the largest animals are not the fastest”, by Myriam Hirt et al, Nature Ecology & Evolution, July 2017
Mr Phelps was merely the latest in a long line of human athletes to have fallen short in physical contests against other species. Most previous competitions involved land-dwelling adversaries, however. In 2007 a South African rugby star sprinted against a cheetah to raise awareness about the decline of the big cat. Two years later an American football player took on an ostrich, the fastest two-legged animal in the world. Both men were soundly beaten. It is unlikely that a human athlete will ever win s
uch a race, given the species’ fastest speeds.
If promoters at Discovery think that a closer contest might help lure even more viewers, they might consult a study published in Nature Ecology & Evolution. It examines the relationship between animals’ size and their maximum velocity. The authors found that the top speed of an animal (or fish) rises in tandem with body mass up to a certain point, after which it declines. Medium-sized animals – such as cheetahs, marlins or hawks – are best for hitting a sweet spot between brawn and energy burst. The smaller Mako shark, it turns out, can swim much faster than the great white.
Geek speak: getting technical
What is a brain-computer interface?
The first computers were large machines that filled entire rooms. As they became cheaper and smaller, they moved out of basements and laboratories and closer to human beings: first to desks and laps, and eventually into pockets and on wrists. So far they have stopped – mostly – at the surface of the human body. But some computers are starting to enter the brain cavity. How would so-called “brain computers” work?
“Brain computer” is a catch-all term for a range of technologies. Definitions diverge depending on where the computer is located, and its level of processing power. Today’s brain computers are relatively simple devices that exist for medical purposes and rely on crude connections to the brain. They are almost always low-power devices worn on the outside of the body, which deliver blunt signals through the skin to relevant regions of the brain. Hundreds of thousands of people already use these machines to bypass conventional input/output systems – such as fingers and voice or eyes and ears – in favour of direct communication with the brain. They are mostly used to make up for a damaged bodily function, such as hearing loss.
