A recent study conducted by the Massachusetts Institute of Technology （MIT） has discovered that river erosion （侵蚀） can lead to increased biodiversity in areas with minimal tectonic（地壳构造的） activity. The researchers focused their attention on the Tennessee River Basin and examined how the erosion of various rock types by the river had led to the separation and diversification of a type of fish called the greenfin darter. As time passed, these separate fish populations evolved into distinct families with genetic differences.

Scientist Thomas Near observed that the greenfin darter was exclusively found in the southern half of the Tennessee River Basin. The researchers analyzed the genes of each fish in Near's data set and constructed an evolutionary tree. This tree helped them comprehend the evolution and differences of the greenfin darter species. They discovered that the fish within the same branch of the river were more closely related to each other than to the fish in other branches.

This study provides evidence that river erosion significantly impacts biodiversity in regions with low tectonic activity. It illustrates how changes in the landscape caused by river erosion can lead to the division and diversification of species over time, even in peaceful environments. These findings enhance our understanding of the mechanisms（机制） that drive biodiversity and evolution, even in areas that are not typically associated with intense tectonic activity.

Subsequently, the team discovered a strong correlation between the habitats of the greenfin darter and the type of rocks present. The southern half of the Tennessee River Basin consists of hard, tightly packed rocks, resulting in turbulent（湍急的） waves in the rivers that flow through it. This characteristic may be favored by the greenfin darter. As a result, the team assumed whether the distribution of greenfin darter habitats had been influenced by the changing rock types, as the rivers eroded the land over time. To test this assumption, the researchers developed a simulation model. Remarkably, the results confirmed their assumption.

Advanced machinery has changed agriculture greatly, but many tasks are still done by hand. Manual pickers can select and handle ripe produce more precisely, which reduces damage, while machines require a lot of upfront (预付的) investment. But in a warming world, farm labour has its own cost in the form of heat stress which can lead to serious diseases.

Data from the EU's Earth monitoring program showed that the seven years before 2022 were the hottest on record. According to one study, at least 65 workers died from heat-related illness on US farms between 2002 and 2021. Another study concluded that American crop workers were 20 times more likely to die as a result of heat stress than other civilian employees.

The average number of unsafe summer working days in the US is expected to double by 2050. The threat is worse in southern Asia and western Africa, where the impact of global warming on human health and productivity is expected to be most extreme. The accumulated global cost in terms of output and working days lost due to heat stress is estimated to reach 2,400 billion dollars by 2030, according to the International Labour Organization.

Some countries have made laws to prevent heat illness. California was the first US state to bring in a large number of rules to protect outdoor workers in 2005. On days above 26 degrees Celsius, employers have to provide shelter for workers during rest periods. When temperatures rise above 35 degrees, workers must have regular breaks. Since the rules came into force, the number of reported deaths from environmental heat exposure in California has fallen from 10 in 2005 to 3 in 2019.

A new federal standard to fight against heat risks across the US is currently in the works (在筹备中). But campaigners say many farm workers, especially immigrants, may be afraid to raise concerns for fear of losing their jobs. They also worry that doctors are unaware of or may fail to recognize the long-term damage from repeated exposure to heat stress, an ongoing threat for millions of agricultural labourers around the world.

Human speech contains more than 2, 000 different sounds, from the common "m" and "a" to the rare clicks of some southern African languages. But why are certain sounds more common than others? A ground-breaking, five-year study shows that diet-related changes in human bite led to new speech sounds that are now found in half the world's languages.

More than 30 years ago, the scholar Charles Hockett noted that speech sounds called labiodentals, such as "f" and "v", were more common in the languages of societies that ate softer foods. Now a team of researchers led by Damián Blasi at the University of Zurich, Switzerland, has found how and why this trend arose.

They discovered that the upper and lower front teeth of ancient human adults were aligned (对齐), making it hard to produce labiodentals, which are formed by touching the lower lip to the upper teeth. Later, our jaws changed to an overbite structure(结构), making it easier to produce such sounds.

The team showed that this change in bite was connected with the development of agriculture in the Neolithic period. Food became easier to chew at this point. The jawbone didn't have to do as much work and so didn't grow to be so large.

Analyses of a language database also confirmed that there was a global change in the sound of world languages after the Neolithic age, with the use of "f" and "v" increasing remarkably during the last few thousand years. These sounds are still not found in the languages of many hunter-gatherer people today.

This research overturns the popular view that all human speech sounds were present when human beings evolved around 300, 000 years ago. "The set of speech sounds we use has not necessarily remained stable since the appearance of human beings, but rather the huge variety of speech sounds that we find today is the product of a complex interplay of things like biological change and cultural evolution," said Steven Moran, a member of the research team.