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Photo Source: Unsplash, did the ancients like to eat bitter meat watermelons?

Watermelons come from the ancient African continent.

As early as 4300 years ago, there was an oval, striped green object on the murals of ancient Egyptian tombs, much like the familiar fruit, watermelon. Moreover, next to the suspected watermelon, grapes and other fruits were painted, so it was easy to believe that people were enjoying the sweet taste of watermelon at that time.

But scientists know that watermelons are not always sweet. Sweet watermelon is not so much a gift from nature as the beautiful result of years of artificial domestication. Before domestication, the flesh of wild species of watermelon was often bitter and even hard to swallow. Many researchers are exploring what kind of unpalatable melon, through what kind of path, evolved into today's delicious watermelon.

On this road, there is a very important question to answer: if watermelons originally taste bitter, why did humans start to plant watermelons and domesticate watermelons? Recently, a group of scientists found an answer when they looked at the seeds of ancient watermelons from 6000 years ago.

You can tell what it tastes like just by looking at the seeds. The Citrullus lanatus we eat today is only one species of the genus Citrullus. It also has several bitter flesh relatives from a relatively distant time and space.

In the 1950s, archaeologists began excavating a site called Uan Muhuggiag in Libya (next to Egypt). In the decades that followed, scientists found a number of plant seeds at the site, as did the oldest watermelon seeds ever found-they are more than 6,000 years old, according to carbon 14 dating.

These Neolithic seeds are important clues to crack the ancestors of watermelons. In addition, the researchers also obtained another set of watermelon seeds from Sudan, which were produced about 3,300 years ago.

Scientists say there is little difference in appearance between different species of watermelon. In order to confirm the genetic relationship between seeds, they need to use genome sequencing to find their similarities and differences.

Of course, it is not enough to have melon seeds from thousands of years ago. If you want to know where the ancestors of modern domesticated watermelons are, you have to compare them with younger samples. As a result, the research team from the Royal Botanical Gardens (Kew Gardens) in the museum, found 47 watermelons (Citrullus lanatus) samples produced between 1824 and 2019, and collected from national studies have been sequenced watermelon species of the genome, in order to find the relationship between old and new melons.

Image source: the sequencing of Miss Qinpu's genome tells scientists that the corresponding set of Libyan seeds 6,000 years ago may have green and white flesh and taste bitter:

The reason why it is presumed to be green and white melon flesh is because of a gene called LYCB, which has a V226F mutation in the red watermelon we eat, but not in ancient Libyan seeds. The reason for the presumption of bitterness is that a bitterness regulatory gene ClBT, the sweet watermelon we eat now, has a non-bitter allele, while Libyan seeds carry bitterness alleles.

In the Sudanese seeds 3, 300 years ago, the researchers did not find the corresponding DNA fragments of the two genes, nor could they tell whether the flesh was sweet or red. If scientists want to understand how the two groups of ancient melon seeds from Libya and Sudan are related to modern watermelon species, and to find out why humans domesticated watermelons, they will have to dig up more clues from the genome.

Why do humans grow it when it is so bitter? When comparing the genomes, the scientists found that the group of Libyan melon seeds 6, 000 years ago was similar to the sticky-seed watermelon (Citrullus mucosospermus) grown in West Africa today. Sticky-seed watermelon also has bitter flesh, which is inedible, but today people grow it not as a fruit, but more often as a snack or stewed in soup.

So, did the ancients also eat bitter watermelon seeds? The Libyan melon seeds were found in a Neolithic human settlement, and the researchers found typical traces on some of the seeds, similar to those of modern watermelon seeds bitten by human teeth.

UMB-6 represents the 6, 000-year-old seeds of Libya (photo source: original paper), which leads scientists to believe that 6, 000-year-old humans were in the habit of eating melon seeds. At that time, people lived a life of hunting and gathering. at the end of a hard day, they might go back to the cave to rest, sit around and chat and eat melon seeds. If it is not to eat melons, but to eat seeds, it is not difficult to understand that bitter watermelons in ancient times will be collected and cultivated by human beings.

In other words, the domestication of watermelons may initially be driven by eating melon seeds, a discovery that surprised scientists.

In addition, the researchers also found that many living species can be found in the genome of Libyan seeds: in addition to the genes of sticky watermelon just mentioned, there are also genes of some subspecies of watermelon (Citrullus lanatus) species that we often eat, as well as genes of Amaru watermelon (Citrullus amarus) from South Africa.

Scientists say there is a clear genetic introgression between Libyan seeds and modern domesticated watermelons (Citrullus lanatus). The so-called gene infiltration refers to the gene flow between two gene pools, which is usually caused by interspecific hybridization. So, the seeds of Libya may not be the wild ancestors of modern domesticated watermelons, and their flesh may not be delicious, but they should already be the product of human domestication.

Original paper:

Https://academic.oup.com/mbe/article/39/8/msac168/6652436

Reference:

Https://source.wustl.edu/2022/08/seedy-not-sweet/

Https://www.pnas.org/doi/10.1073/pnas.2101486118

Https://leicester.figshare.com/articles/journal_contribution/Ancient_agriculture_in_Libya_a_review_of_the_evidence_/10088354

Https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4512189/

Https://academic.oup.com/aob/article/116/2/133/180059

Https://www.smithsonianmag.com/science-nature/watermelon-seeds-were-snacked-before-its-flesh-became-sweet-180981008/

Https://www.nationalgeographic.com/history/article/150821-watermelon-fruit-history-agriculture

Source: science Popularization China-Star Project (creation and cultivation)

This article comes from the official account of Wechat: global Science (ID:huanqiukexue), written by: chestnut, revision: clefable

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