As it turns out, animals and fungi share a common ancestor, and branched away from plants at some point about 1.1 billion years ago. It was only later that animals and fungi separated, taxonomically speaking.
Think back to the last time you took a stroll through a dense, overgrown forest. You probably saw all different varieties of plant life—vines, bushes, moss, trees, and a healthy number of fallen logs. A forest is one of the best places to see the circle of life at its most beautiful, which is when life balances with death.
When things die in nature, they begin to break down and decompose, which is where fungi come into play. Fungi belong to a kingdom all their own, just like animals, plants, monera (bacteria), and protista (algae).
Fungi are eukaryotic organisms that absorb nutrients from other organic matter. When a tree falls or an animal dies, fungi are typically the first on the scene to begin the natural process of decomposition.
Upon seeing a mushroom, most people would immediately view it as a vegetative organism, one that is closely related to plants. However, as recent research has shown, mushrooms are in fact more closely related to humans than plants!
The Classification of living organisms
Humans have always been fascinated by life in all its forms, but thousands of years ago, we classified life on Earth into only two categories: plants and animals. We can thank Aristotle for that, who further divided animals into those with and without blood, as well as those in the land, sea, and air.
That rudimentary system remained in place until the 1600s. In the 18th century, Carol Linnaeus divided life into the kingdoms of animals and plants, and then further began dividing those into different genera and species, which is why we have a two-part naming system in science (Homo sapiens, for example; Homo is the genus and sapiens is the species).
It wasn’t until the middle of the 19th century that single-celled organisms were finally given their due as a separate kingdom of life (Protista). Seventy years later, single-celled organisms were divided into eukaryotes and prokaryotes, so bacteria became the 4th kingdom of life. Although fungi had been recognized as a unique part of the animal kingdom, it was not separated into its own kingdom until 1969. This five-kingdom system remains the most widely accepted format for classifying life on Earth.
All classifications of life, until recently, including the expansion from two kingdoms to five, were based on physical observations of how things looked, even under a microscope. This is how the closeness and relationships between species, genera, classes, orders and kingdoms were decided. Given that fact, it comes as no surprise that most people classified fungi as plants for so long. The similarity in appearance is pretty clear; after all, some of them so look like little red and white trees…
Using similarities in DNA to classify organisms
However, thanks to modern technology, the analysis of genetic relationships between species and organisms is now possible, and has led to looking at relationships between forms of life differently. In 1990, Carl Woese suggested the ‘Three-domain system’ of classification based on genetic similarities between organisms. The system shows a common ancestor of all life that divides into three broad domains—Bacteria, Archaea, and Eukaryotes (the organisms with a nucleus to store their DNA).
By examining the genes of different species, both animal and fungi, mutational changes can be observed, and genealogical relationships can be determined that stretch back millions of years.
As it turns out, animals and fungi share a common ancestor and branched away from plants at some point about 1.1 billion years ago. It was only later that animals and fungi separated on the genealogical tree of life, making mushrooms more closely related to humans than plants. Most likely, this common ancestor was a single-celled organism that had sperm-like characteristics (like an animal) and then a later developmental stage with a stronger cell wall (fungi).
Image Caption: A phylogenetic tree based on rRNA analysis. On the right hand side, notice the divergence of plants, fungi and animals.
Are mushrooms vegetables?
Simple answer? No, a mushroom is not a vegetable. Mushrooms are fruiting bodies of macroscopic filamentous fungi. Earlier, when mycology (the study of fungi) first arose, it was a part of botany. This happened because fungi were considered to be primitive plants.
The major difference between a plant (vegetable) and a mushroom is how they acquire their food. In the case of plants, they possess chlorophyll and make their food via photosynthesis. Fungi, on the other hand, exist on decaying material in nature. Also, there are the obvious structural differences, such as a lack of leaves, roots, and seeds. Thus, fungi now have their own kingdom on the basis of cellular organization.
However, this is the science side of things, but let’s take a look at the other side—food! In daily life, we don’t use science to classify our food. Tomatoes and cucumbers are scientifically the fruits of a plant, but we still call them vegetables. It’s a similar story with mushrooms. They aren’t vegetables or fruits or even meat. They are a different category in and of themselves, but for the sake of convenience, we lump them together with vegetables.
Regardless of categories, mushrooms have been proven to help in maintaining overall wellbeing and vitality in humans. There are different kinds of mushrooms that have various health benefits. At one point in history, mushrooms were so highly regarded that it was actually forbidden for the common folk to eat them! They were reserved only for royal families.
The Mushrooms and Men have similar DNA
Haven’t you ever noticed that eating a perfectly cooked portobello mushroom feels a lot closer to eating meat than a salad? Well, that isn’t exactly a scientific explanation of the connection, but genetic studies show that there might a common ancestor from which both animals and fungi evolved.
In 1993, researchers Baldouf and Palmer published a paper ‘Animals and fungi are each other’s closest relatives: congruent evidence from multiple proteins’. They compared 25 proteins and their DNA sequences between bacteria, plants, animals, and fungi. They found that animals and fungi had similarities in certain proteins that plants and bacteria did not. As the researchers write in their paper “This congruence among multiple lines of evidence strongly suggests, in contrast to traditional and current classification, that animals and fungi are sister groups, while plants constitute an independent evolutionary lineage.”
A 2005 paper described how both animals and fungi are relatives of protists through protein analysis. Researchers are still teasing out the complex relationships between animals and fungi, but there is enough evidence to suggest that you and a mushroom have more in common than a plant has with a mushroom.