Cichlids, beloved friends of Open Code, are perplexing fish due to their evolutionary talent. Many of the colorful fish purchased for aquariums belong to this freshwater family, despite not appearing to be related at all. New species are described each year, making it difficult to determine their affiliation with this extraordinarily prolific family. Cichlids range in size from the small hermit cichlid, which is the size of a paracetamol and lives in abandoned snail shells, to the Emperor cichlid, which can grow as large as a hake. Their diversity of shapes and geometric colorations is simply astonishing, as is the speed at which they have generated this biodiversity.
In order to understand the evolutionary timeline of cichlids, we must establish an internal clock to put it into perspective. One common trick is to equate the 4.5 billion years of Earth’s existence to one year of our lives: January 1st is the formation of the planet, and December 31st is today. In this scale, the first bacteria emerged in early March, modern cells (eukaryotes) in mid-May, and the first animals in October. Despite our significant impact on the environment and our species’ self-importance, humans have only been around for 10 minutes. We must prepare for the New Year’s Eve countdown.
Cichlids are not new by any means. They appear in the fossil record around December 25th, with genetic evidence supporting an even earlier existence. In this small geologic timeframe, the mother of all cichlids has generated 1,700 known species, making them the most diverse family of vertebrates on the planet. In the three large African lakes—Malawi, Victoria, and Tanganyika—cichlids have not only separated into different species within each lake but also within different regions of the same lake. In Lake Tanganyika alone, 240 species have evolved with incredible morphological diversity. This lake is relatively young, meaning this evolutionary spectacle occurred in a short geologic timespan. Many species in African lakes likely appeared within the last 10,000 years, a mere fraction of our timeline.
What makes cichlids truly unique has recently been discovered by scientists. The ancestral species of cichlids, which gave rise to this prodigious variety, underwent a mutation that made them prone to exploring new environments. Lake Tanganyika formed on December 30th due to a rapid flood that filled a massive rift valley fracture (30,000 square kilometers). Some cichlids from nearby rivers were carried in by the water and, true to their exploratory genetics, explored every nook and cranny of the new lake, adapting to rocky bottoms, sandy shores, different plants, food sources, prey, and varying conditions. The lake’s diverse habitats combined with the cichlids’ exploratory nature to create biological architectures never seen before.
While some may speculate on the future of political leaders like Pedro Sánchez, the true exploration lies with the cichlids in their infinite variety. The world may be forever changed by their evolutionary journey.
