EVERYONE WAS WRONG ABOUT AVOCADOS...?

EVERYONE WAS WRONG ABOUT AVOCADOS

If you happen to be a fan of avocados - and let's be honest, who isn't? - you may have come across the notion that these delicious fruits owe their existence to giant ground sloths from prehistoric times. This idea has been circulated by us here at SciShow, but let's delve into the details. According to the story, plants evolved to produce fruit as a means of attracting animals. These animals would then consume the fruit and subsequently disperse the seeds through their droppings, aiding in the spread of the plant species. Unlike other fruits with small seeds, avocados possess large seeds. This suggests that they were likely spread by large animals capable of swallowing the entire seed, such as the giant ground sloths that once roamed North and South America during the Pleistocene era. It sounds plausible, right? Well, as it turns out, there is no concrete evidence to support this claim. Despite the widespread popularity of this myth, it is important to examine the true origins of avocados in order to uncover the kernel of truth. So, where did this idea of giant ground sloths dispersing avocados come from? The story begins in the 1980s with a scientific paper proposing a new hypothesis regarding Costa Rican plants. This paper briefly mentioned the role of large animals as seed dispersers, but did not specifically reference sloths or avocados. In the same year, another paper speculated that this concept could be applied to avocados and pointed towards ground sloths as potential dispersers. However, it is crucial to note that neither of these papers presented any actual data on sloths or avocados. It seems that publishing papers was relatively easier in the 1980s. In the 2000s, a popular science book further popularized this narrative, despite the lack of substantial evidence And extensive. And then the concept just became ingrained. It has been widely discussed and written about for many years. Numerous platforms have published articles about this interesting fact, and as I mentioned earlier - we even created a video about it a few years ago! However, there has never been a single study or project that has found any evidence of sloths consuming avocados. So, what would we need to discover in order to prove a connection? What is the definitive proof that sloths ate avocados, and how would we go about finding it? Well, it's all about science! There are several types of evidence we could search for to establish avocados as part of sloths' diet. Firstly, and this may seem obvious, sloths and avocados would need to have coexisted in the same geographical area during the same time period. Therefore, we would need to uncover fossilized remains of both species in the archaeological record dating back between 2.58 million years ago and 11,700 years ago, which is approximately when the last ground sloths became extinct. It would be even more compelling if we could find traces of avocado in sloth coprolites, which are fossilized feces, as this would confirm that sloths actually consumed the fruit. However, we currently have no evidence of either of these things. Fossilized bones and feces of ground sloths, including Mylodons and Lestodons, have been found predominantly in South America during the Pleistocene era, specifically in what is now Argentina, Uruguay, and Paraguay. On the other hand, the first true avocados had only recently appeared in Southern Mexico around that same time. There were some other ancient species of ground sloths whose droppings were discovered closer to the region where avocados originated, such as the slightly smaller but still massive Nothrotheriops genus. However, even if these sloths lived in the same area and time period, it does not necessarily mean that they consumed avocados. For example, I live in the same area and time as poison ivy, but I do not eat poison ivy, and I never would. Determining the exact diet of these ancient sloths is a complex task. In a 2011 study, researchers analyzed the proportions of carbon and nitrogen in Lestodon bones and concluded that the giant sloths primarily fed on leafy plants. They might have consumed fruits in addition to that; however, the test cannot determine which parts of the plant the animals consumed. Coprolites left by a smaller sloth species in a cave in Cuchillo Curá, Argentina, revealed remnants of mostly grasses and sedges. Other samples of sloth feces indicated that the larger sloths consumed grasses and shrubs, similar to those from the same family as carrots and parsley. Nothrotheriops dung contained fragments of yucca and agave plants. None of these studies found any trace of DNA from laurel plants, which avocados belong to. Newer methods also allow us to examine the front end of the sloth for information about their diets. Archaeologists analyzed a tooth from the Pan-American giant ground sloth, which lived during the late Pleistocene. By analyzing the relative amounts of carbon and oxygen isotopes in the layers of the tooth, researchers reconstructed its diet throughout the year and discovered that it had a varied diet depending on the availability of shrubs and plants. Although we cannot determine the exact types of plants this sloth consumed, based on climate data, it likely consumed shrubs like juniper. What's even more astonishing is that some ancient sloths may not have limited themselves to a plant-based diet. Carbon and nitrogen analysis of their hair suggests that Darwin's ground sloth probably consumed meat, although we are not completely certain whether it was a slow-moving hunter or simply a scavenger. This opens up the possibility that other sloths could have also consumed meat. Therefore, while we have extensive data on the diets of ground sloths, none of it indicates any connection to avocados. Additionally, there is another significant flaw in the argument regarding megafauna. Avocados may not have required massive animals at all. Avocado pits from approximately 10,000 years ago were only half the size of today's seeds, measuring around 2 centimeters wide compared to the 5.5 to 6 centimeters commonly found in grocery stores. Therefore, if the avocado pits started out smaller, it suggests that they did not rely on large animals for dispersal. There must be a more plausible explanation for these enormous cavities that does not involve our slow-moving colossal companions. Interestingly, the most probable culprit appears to be a different large mammal residing in Mexico - humans! It appears that avocados served as a significant source of sustenance for the people in Mesoamerica, who began cultivating them in their gardens in the Tehuacán-Cuicatlán Valley approximately 10,000 years ago. As previously mentioned, archaeological evidence indicates that the size of the pits has increased over time. This suggests that the Mesoamericans may have deliberately chosen avocados with larger pits. Perhaps larger pits signified larger fruits or aided in the tree's growth. A substantial seed filled with starches and fats could nourish the plant during germination, increasing the likelihood of a planted seed developing into a fruitful tree. However, the reason behind these colossal pits may be just as much rooted in mythology as it is in botany. According to ancient Mayan beliefs, individuals were believed to be reborn as trees, leading them to surround their homes with fruit trees. Avocado fruits became associated with strength, and it was believed that consuming them would transfer this strength to the person. Consequently, cultivating larger avocados also meant acquiring more strength. Nevertheless, determining precisely how and when these pits grew larger remains somewhat challenging.