Scientists have long believed that fertile soil was man-made, although there is no way to prove it.
But in recent months, extensive fieldwork and studies in the Amazon region have yielded compelling evidence that these suspicions are true. Scientists say their discovery could change everything we know, not only about the region and its history, but also about organic matter that is vitally important to human well-being.
A body of research has revealed the extent of our ancestors' connection to the land, specifically the ancient inhabitants of the Amazon, who deliberately created fertile "black" land, or as it is called "terra preta."
The phrase "terra preta" literally means "black soil" in Portuguese, and such soil is found in many areas but in particularly dense quantities around former human habitation.
In a joint study from the Massachusetts Institute of Technology (MIT), the University of Florida and the Federal University of Santa Catarina, several scientists combined soil analyses, ethnographic observations and interviews with modern indigenous communities to conclude that Terra Preta was intentionally created by ancient Amazonians.
“This could change everything,” Lucas Silva, an ecologist at the University of Oregon who was not involved in the new study, told Science.
“We see here that people played a role in creating the Black Earth, intentionally modifying the ancient environment to make it a better place for humans,” added Taylor Perron, the Cecil and Ida Greene Professor of Earth, Atmospheric and Planetary Sciences at MIT.
Black earth contains large amounts of stored carbon collected over hundreds to thousands of years. As each generation enriches the soil with food scraps, charcoal and waste, it becomes more concentrated in natural resources.
What has caught scientists' attention is unintended carbon sequestration. They say it can be used as a way to mitigate the negative effects of climate change.
“We may be able to adapt some of their local strategies on a larger scale to sequester carbon in the soil in ways that we now know will remain there for a long time,” Samuel Goldberg, a co-author of the study, wrote in the journal Science Advances.
Crops grow much better on black soil because it is rich in phosphorus, nitrogen and calcium content.
These soils are usually found near archaeological sites and contain charcoal, organic matter from food remains such as fish and animal bones, in addition to artefacts such as pottery shards. All of this indicates that ancient civilizations were intentionally adding these elements to the soil and making it fertile, which in itself is an extraordinary discovery, if true.
Morgan Schmidt, an archaeologist and geographer at the Federal University of Santa Catarina, and his team studied the soil in the Quikuru indigenous territory, on the upper Xingu River in the southeastern Amazon, Brazil.
There, they analyzed soil from four archaeological sites and two historic villages that were occupied from 1973 to 1983. They also looked at one modern village, known as Koikuru 2.
Radiocarbon dating of the lands found that the oldest sample was 5,000 years old, while the other samples ranged from 300 to 1,000 years old.
By collecting soil from hills adjacent to ancient and historic villages, scientists compared it to terra preta soil, and found that soil from residential areas contained more than twice as much organic carbon and was less acidic, making it more fertile. When they analyzed soil from Koikuru 2, the team found a similar pattern.
The results will be vital in better understanding not only the rich cultural and historical practices of the people of the Amazon Basin but also the future of humanity.
“Modern sustainable agriculture and climate change mitigation efforts, inspired by the enduring fertility of the ancient Black Earth, could build on traditional methods practiced by Amazonian indigenous people to this day,” the study concluded.
What happens when the sperm reaches the egg?!
A new study conducted by ETH Zurich University in Switzerland and Ludwig Maximilian University in Germany has revealed the complexities of a special protein compound known for its crucial role in the fertilization process.
The researchers revealed chemical changes that occur in the egg membrane the moment the sperm slides toward it. Minutes after the sperm unites with the egg, the fertilized egg releases charged zinc atoms that are thought to prevent other sperm from entering the egg by hardening its outer shell.
But the details of these precise molecular events have not been fully studied.
In this regard, Paulina Bakak, a bioinformatician at ETH Zurich and first author of the study, said: “It was hypothesized that combining the two proteins “JUNO and IZUMO1” in a single complex leads to the initiation of the process of recognition and adhesion between progenitor cells, thus enabling their fusion.”
The interaction between JUNO, located on the outer membrane of the female egg cell, and IZUMO1, located on the surface of the sperm cell, is the first known physical link between two newly merging sex cells.
But scientific efforts to develop a potential method of contraception by creating small molecule inhibitors of the JUNO-IZUMO1 recombination process have been largely unsuccessful, revealing further uncertainty about their molecular interactions.
The research team explained that the synthesis of proteins occurs constantly inside cells, where they float in a watery mixture of the cytoplasm and reactions occur as they are recycled. So, the research team used a Swiss supercomputer to simulate the interactions between JUNO and IZUMO1 in water, closer to their natural forms in cells.
The simulation showed that a combination of short-lived and weak interactions between protein molecules led to the stabilization of the JUNO-IZUMO1 complex.
Next, we simulated the destabilization of the interactions holding JUNO-IZUMO1 together by zinc ions released by the egg.
It turns out that the presence of zinc ions caused IZUMO1 to recoil, so it could no longer bind strongly to JUNO. What reveals that the release of zinc by the egg can hinder the attachment of other sperm to it.
While this is just a computer simulation based on protein sequences and shapes, the results provide new insight into the first moments of fertilization.
The study was published in Scientific Reports.