In the history of life on Earth, a dramatic and revolutionary change in the nature of the sea floor occurred in the early Cambrian (541–485 million years ago): the “agronomic revolution.” This phenomenon was coupled with the diversification of marine animals that could burrow into seafloor sediments. Previously, the sea floor was covered by hard microbial mats, and animals were limited to standing on, resting on, or moving horizontally along those mats. In the agronomic revolution, part of the so-called Cambrian Explosion of animal diversity and complexity, vertical burrowers began to churn up the underlying sediments, which softened and oxygenated the subsurface, created new ecological niches, and thus radically transformed the marine ecosystem into one more like that observed today.
This event has long been considered to have occurred in the early Cambrian Period. However, new evidence obtained from western Mongolia shows that the agronomic revolution began in the late Ediacaran, the final period of the Precambrian, at least locally. Paper. (public access) – Tatsuo Oji, Stephen Q. Dornbos, Keigo Yada, Hitoshi Hasegawa, Sersmaa Gonchigdorj, Takafumi Mochizuki, Hideko Takayanagi, Yasufumi Iryu. Penetrative trace fossils from the late Ediacaran of Mongolia: early onset of the agronomic revolution. Royal Society Open Science, 2018; 5 (2): 172250 DOI: 10.1098/rsos.172250
As noted earlier, it’s not clear how much evolution of basic animal behaviour there has been in the last 550 million years.
See also: Earlier than thought: Worm burrows at rock layers over 600 million years ago
Cambrian fossil shows parent caring for young