Understanding the Complex Web of Life on Earth

On planet Earth, biodiversity – the variety of life – is our ‘hidden universe. Its components are far more abun-dant, numerous, complex and interwoven than most people may realise. In Africa, our ancestors began to explore biodiversity very early on in our evolutionary history and were guided by the most basic needs of food, shelter and comfort. For hundreds of thousands of years, they tasted most things they came across. They used their senses to explore the plants growing around them and observed what other animals ate. They discovered that some plants had edible roots, but the leaves would make them sick, some plants produced sweet juicy fruits while others were bitter, and some plants were best avoided at all costs. They gradually increased their diet to include many different parts of plants, fungi, mammals, birds, fish, insects and spiders. They learned which trees provided the best wood for making fires, which animals had the best fur for keeping them warm, and which fruits were most delicious.

As our human ancestors left eastern Africa and reached other parts of the world, they made new discoveries. On every continent, the exploration of nature began immediately after their arrival. There was often abundant prey, but they had to learn how to hunt it, or satisfy themselves by scavenging on carcasses. They gathered many different sorts of nuts and berries. In some places, animals were easier to catch but fewer in number, like in the Indonesian island of Flores. The island is so tiny and food resources so limited that, when our human relatives arrived there about a million years ago, natural selection consistently benefited small individuals, leading to the evolution of a separate species.

An adult Homo floresiensis was only about a metre tall (3.3 feet), which is shorter than most humans with dwarfism today and about the same size as the island’s own species of dwarf elephant. In the Levant, another relative of ours, Homo erectus – which inhabited many parts of Africa and Eurasia for some 1.5 million years – relied on elephants, hippos, rhinos and other large animals as a source of a fat-rich diet.

As the brain size and cognitive abilities of our ancestors increased, they became increasingly better at developing tools for hunting and processing plants and animals. The development of thousands of local languages allowed them to communicate what they had discovered about the species around them and their uses. In China, archaeological evidence for herbal medicines began some 8,000 years ago. By 4,000 years ago, the Sumerians had left written accounts demonstrating their use of plants like cumin, mint and liquorice.

While most information associated with species was passed around by word of mouth, the Greeks attempted to synthesise all knowledge available at the time. In the fourth century BCE, Aristotle wrote down everything that was known to him about animals. Shortly after that, his apprentice Theophrastus did the same, but focusing on plants. Knowledge about species continued to grow, and discoveries piled up. Farmers experimented with ever more species, which increased the nutritional value of our diet and the range of climates and regions in which we could grow food. Traditional Chinese medicine – charac-terised by the prescription of many different plants and animals to treat all sorts of ailments – became increasingly popular across much of eastern Asia.

However, by the time western societies entered the Scientific Revolution of the seventeenth and eighteenth centuries, things had got messy. No comprehensive summaries of plant and animal knowledge had been written in Europe for almost 2,000 years, and people from different countries struggled to communicate their knowledge about species. Even when they could use the same language – usually Latin, among scientists – they didn’t have a standardised way to name species. The dog rose – a common wild rose in Europe, whose fruits can be turned into a nutritious soup if you dry them and remove the hairy seeds – would be called Rosa sylvestris inodora seu canina by one person and Rosa sylvestris alba cum rubore, folio glabro by another. Not only was it a burden to learn all the different names a species could have, but also those names were often long and awkward. Misunderstandings were common and could be disastrous. In the carrot family, for instance, some of our best foods and spices – including carrots, celery, anise, coriander and parsley – could easily be confused with some of the most poisonous wild plants known, due to their similar flowers and leaves.

Given so many unknowns and constant discoveries, it is perhaps not surprising that the total number of species on Earth is, at most, what we can call an informed guesti-mate. There are currently c.3.5 million species scientifically described. Of these, scientists believe that about half are synonyms – those described more than once and so having two or more names, in which case only the first description and name is considered legitimate. This leaves a total of 1.8 million ‘valid’ species.

Today, many biologists I know seem content with the estimate that c.8.7 million species live on land and in the sea. But this may be more a sign of their lack of interest in speculating about something no one can really prove right now. One thing is certain: this number will change, and will most probably increase. Technological developments over the last few decades have allowed us to detect ever smaller species, and those that are very rare or specialised. We’re now assessing the biodiversity of places we couldn’t previously access, from thermal vents in the deep ocean to the dense forests of Papua New Guinea. As scientists, we are also increasingly encountering unknown species in our own biological collections, such as fungi living exclusively within the seeds of certain plants, or the lichens and mosses on leaves and branches of herbarium specimens.

Further, the 8.7 million estimate excludes a significant and substantial portion of all diversity: bacteria and Archaea. For both of these groups, species’ boundaries and definitions are less clear. Once you include these two groups, serious calculations suggest that a trillion (!) species might in fact share this planet with us. As a comparison, the Milky Way is estimated to contain some 100-400 billion stars. This shows the level of discovery and understanding that lies ahead of us.

Source : The Hidden Universe: Adventures in Biodiversity by Alexandre Antonelli

Goodreads : https://www.goodreads.com/book/show/56669607-the-hidden-universe