What Is Phylogeny?
Surely you have ever made a family tree at school. Looking for how to draw it, we have all investigated at some point where our ancestors came from or, for example, why do we have brown eyes if our grandfather had them sky blue.
All this leads us to the question that occupies us today: what is phylogeny? Or, put another way, what happens when, instead of making a family tree, scientists decipher the evolutionary path of a species? What scientific discipline should we focus on if we want to find the first living being that populated the planet?
In the following lines we tell you what family trees, blue eyes and Mendel’s peas have to do with each other. Read on to find out.
What is phylogeny?
Phylogeny is the branch of evolutionary biology that studies the origin of life, that is, the kinship relationship between species throughout evolution. The objective is to build a phylogenetic tree that indicates who are the ancestors of a specific species. The word was coined by the German naturalist and philosopher Ernst Haeckel in the late 1800s.
As we already know, evolution is such a slow process that an individual does not live long enough to see it with their own eyes. To this day, it is popular knowledge that birds are the descendants of dinosaurs, but how was that conclusion reached? There are two main ways to determine the phylogeny of a species:
- Morphological phylogenetics: investigates the relationships between living beings through the similarities between their morphology. It is especially useful for finding convergences between fossilized and current species.
- Molecular phylogenetics: tries to determine the relationships between species through the study of DNA, RNA and proteins. When the nucleotide and amino acid sequence of two species is sufficiently similar, they are considered to have a common ancestor.
The human phylogeny
How many times have we heard that we come from the monkey? The human, the first to consider what phylogeny is and how to apply it, took his own species as one of his main objectives, of course. However, it seems that, no matter how similar we are to the great apes, our origin is not the same.
The answer to the question about our origin is, obviously, yet to be discovered: when did the human begin to be human? Chris Stringer, one of the UK’s most renowned anthropologists, has dedicated his career to answering this question.
Stringer is one of the most staunch defenders of the theory that the human species as we know it originated on the African continent, migrating from there to Europe and Asia and gradually replacing the hominids that lived there, such as Homo erectus and homo neanderthalensis.
In order to further this hypothesis, three tests were presented in favor:
- The genetic markers examined by paeleontologists vary much more in this ancestral African species. This genetic variation is reduced as we move away from Africa.
- In phylogenetic trees, the separation between African and non-African species of humans is the oldest known.
- In addition, it has also been found that the time of separation of both species coincides with the estimated dates for the beginnings of homo sapiens.
However, the old theory that Homo erectus and Neanderthal were banished from their lands lost steam when it was shown that there were inter-species crosses. The most recent DNA studies show that we do indeed inherit characteristics from these two species.
The Tree of Life
Despite the fact that phylogeny as such was born with Haeckel, C harles Darwin was the one who introduced the concept of evolution, with his studies on adaptive changes in the morphology of different species.
The ultimate goal of phylogeny is, therefore, to complete the tree of life, the phylogenetic path of all the species present on planet Earth. In it, the root would be the primeval species from which we all come, and the last branches, the current species.
Who then occupies the position of last universal common ancestor? Known as LUCA— Last Universal Common Ancestor in English—, this position is held by cyanobacteria. Other theories say that, being a kingdom in itself – they are not animals or plants – the oldest creature is the sea sponge, with more than 750,000 years on Earth.
All this leaves us with a clear question: who will be the next LUCA? Will we ever reach the roots of our existence? We can only hope we live to find out.
