High pollution linked to unhappiness among Chinese people, MIT researchers say

Who would've thought that never seeing blue sky would bum you out?

  • China's economy is growing at 8 percent per year, but its citizens aren't getting any happier.
  • New research from MIT analyzed 33 million posts from Sina Weibo (the Chinese version of Twitter) and compared their expressed happiness with local pollution levels.
  • The study shows that high-pollution days are making Chinese civilians significantly less happy.

As London industrialized in the 19th and 20th centuries, it produced fog—a lot of it. On particularly bad days, London was choked with a thick, yellow-green gas that could kill, making for a fairly miserable climate. So much so, poet and playwright Oscar Wilde once said, "London is too full of fogs and serious people. Whether the fogs produce the serious people, or whether the serious people produce the fogs, I don't know, but the whole thing rather gets on my nerves."

Now, MIT researcher Siqi Zheng may have an answer for Oscar Wilde: air pollution does actually make people more or serious, or at least less happy. But London's air has improved over the years — instead, Zheng looked at China, one of the foggier spots on 21st-century Earth.

Prior studies have looked at self-reports of people's happiness and compared them with air pollution, but these reflections occur after pollution peaks and tend to reflect people's overall happiness. Zheng and colleagues wondered if there was a better way to determine how much pollution impacted happiness in the moment. Fortunately, human beings love to talk about themselves. Today, people's self-expression happens the most on social media programs, so Zheng turned to Sina Weibo, China's version of Twitter. This turned out to be a very rich source of data — Zheng's sample size consisted of 33 million posts from 589,000 users.

Measuring pollution was a fairly straightforward task. China's Ministry of Environmental Protection releases a daily Air Quality Index, or AQI, which measures the main pollutants in each city. In addition to looking at the AQI, Zheng also focused on a class of pollutants that the Chinese are particularly concerned about, PM2.5. (or particulate matter smaller than 2.5 micrograms) has been the most common form of pollutant in China in recent years, and its small size enables the particles to stay in the air longer and bypass the nose or even masks to enter the body and contribute to disease and poor health outcomes.

However, matching air pollution to sentiment was slightly more difficult. It obviously would have been too much work to go through 33 million posts and assess whether they express happiness or not. Fortunately, machine-learning algorithms are able to sift through huge amounts of text, process people's language, and spit out a measurement of how much happiness each post expressed. Zheng and colleagues used a happiness index on a scale of 0 to 100 to quantify the posts' average happiness and used each posts' geotag to match it to local areas with high or low pollution. What's more, they used two different machine-learning algorithms to compare the measurements and ensure that their results weren't simply because of some flaw in their algorithm.

These two charts show a) the density and distribution of Sina Weibo posts used in the study and b) the relationship between overall happiness and the level of PM2.5 on a given day. Image source: Zheng et al., 2019

What they found should come as no surprise. There was a significant negative correlation between happiness and pollution. The results, however, became a bit more nuanced as they dove deeper. Women tended to be unhappier on high-pollution days than men. And, when a high-pollution day fell on a weekend or a holiday, Sina Weibo posts expressed much more unhappiness. After all, having to cancel your social plans because of high pollution isn't likely to put a smile on your face.

In China, pollution causes 1.1 million people to die prematurely each year and costs their economy $38 billion. Despite this loss, China keeps chugging along, growing at an astounding 8 percent per year. But this growth doesn't seem to really be making people happy. It produces pollution, significantly impacting people's quality of life. And, when people are miserable, they tend to act irrationally. Prior research had suggested that people act out in impulsive and risky ways on high-pollution days. Hopefully, research such as Zheng's will give the Chinese government some impetus to reduce pollution: if not to make people's lives better, then to prevent the high costs associated with high pollution.

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New fossils suggest human ancestors evolved in Europe, not Africa

Experts argue the jaws of an ancient European ape reveal a key human ancestor.

Surprising Science
  • The jaw bones of an 8-million-year-old ape were discovered at Nikiti, Greece, in the '90s.
  • Researchers speculate it could be a previously unknown species and one of humanity's earliest evolutionary ancestors.
  • These fossils may change how we view the evolution of our species.

Homo sapiens have been on earth for 200,000 years — give or take a few ten-thousand-year stretches. Much of that time is shrouded in the fog of prehistory. What we do know has been pieced together by deciphering the fossil record through the principles of evolutionary theory. Yet new discoveries contain the potential to refashion that knowledge and lead scientists to new, previously unconsidered conclusions.

A set of 8-million-year-old teeth may have done just that. Researchers recently inspected the upper and lower jaw of an ancient European ape. Their conclusions suggest that humanity's forebearers may have arisen in Europe before migrating to Africa, potentially upending a scientific consensus that has stood since Darwin's day.

Rethinking humanity's origin story

The frontispiece of Thomas Huxley's Evidence as to Man's Place in Nature (1863) sketched by natural history artist Benjamin Waterhouse Hawkins. (Photo: Wikimedia Commons)

As reported in New Scientist, the 8- to 9-million-year-old hominin jaw bones were found at Nikiti, northern Greece, in the '90s. Scientists originally pegged the chompers as belonging to a member of Ouranopithecus, an genus of extinct Eurasian ape.

David Begun, an anthropologist at the University of Toronto, and his team recently reexamined the jaw bones. They argue that the original identification was incorrect. Based on the fossil's hominin-like canines and premolar roots, they identify that the ape belongs to a previously unknown proto-hominin.

The researchers hypothesize that these proto-hominins were the evolutionary ancestors of another European great ape Graecopithecus, which the same team tentatively identified as an early hominin in 2017. Graecopithecus lived in south-east Europe 7.2 million years ago. If the premise is correct, these hominins would have migrated to Africa 7 million years ago, after undergoing much of their evolutionary development in Europe.

Begun points out that south-east Europe was once occupied by the ancestors of animals like the giraffe and rhino, too. "It's widely agreed that this was the found fauna of most of what we see in Africa today," he told New Scientists. "If the antelopes and giraffes could get into Africa 7 million years ago, why not the apes?"

He recently outlined this idea at a conference of the American Association of Physical Anthropologists.

It's worth noting that Begun has made similar hypotheses before. Writing for the Journal of Human Evolution in 2002, Begun and Elmar Heizmann of the Natural history Museum of Stuttgart discussed a great ape fossil found in Germany that they argued could be the ancestor (broadly speaking) of all living great apes and humans.

"Found in Germany 20 years ago, this specimen is about 16.5 million years old, some 1.5 million years older than similar species from East Africa," Begun said in a statement then. "It suggests that the great ape and human lineage first appeared in Eurasia and not Africa."

Migrating out of Africa

In the Descent of Man, Charles Darwin proposed that hominins descended out of Africa. Considering the relatively few fossils available at the time, it is a testament to Darwin's astuteness that his hypothesis remains the leading theory.

Since Darwin's time, we have unearthed many more fossils and discovered new evidence in genetics. As such, our African-origin story has undergone many updates and revisions since 1871. Today, it has splintered into two theories: the "out of Africa" theory and the "multi-regional" theory.

The out of Africa theory suggests that the cradle of all humanity was Africa. Homo sapiens evolved exclusively and recently on that continent. At some point in prehistory, our ancestors migrated from Africa to Eurasia and replaced other subspecies of the genus Homo, such as Neanderthals. This is the dominant theory among scientists, and current evidence seems to support it best — though, say that in some circles and be prepared for a late-night debate that goes well past last call.

The multi-regional theory suggests that humans evolved in parallel across various regions. According to this model, the hominins Homo erectus left Africa to settle across Eurasia and (maybe) Australia. These disparate populations eventually evolved into modern humans thanks to a helping dollop of gene flow.

Of course, there are the broad strokes of very nuanced models, and we're leaving a lot of discussion out. There is, for example, a debate as to whether African Homo erectus fossils should be considered alongside Asian ones or should be labeled as a different subspecies, Homo ergaster.

Proponents of the out-of-Africa model aren't sure whether non-African humans descended from a single migration out of Africa or at least two major waves of migration followed by a lot of interbreeding.

Did we head east or south of Eden?

Not all anthropologists agree with Begun and his team's conclusions. As noted by New Scientist, it is possible that the Nikiti ape is not related to hominins at all. It may have evolved similar features independently, developing teeth to eat similar foods or chew in a similar manner as early hominins.

Ultimately, Nikiti ape alone doesn't offer enough evidence to upend the out of Africa model, which is supported by a more robust fossil record and DNA evidence. But additional evidence may be uncovered to lend further credence to Begun's hypothesis or lead us to yet unconsidered ideas about humanity's evolution.