News

02.02.2017 08:51

Oldest fossil in the human family tree discovered

Humans now have a new great-great-great-ancestor – a bag-shaped, 535 million year old pipsqueak without an anus. An international research team discovered the fossil, which forms part of the base of the deuterostomes, a branch of the tree of life to which humans also belong. The research results have been published online in the renowned scientific journal Nature. One of the authors is the Chinese palaeontologist Dr. Qiang Ou, who also is active as a visiting researcher at the University of Kassel.

A reconstruction of Saccorhytus coronarius from a ventral perspective. Picture credit: Dr. Jian Han

Since July 2016, Dr. Qiang Ou, 39, has been a Humboldt Fellow in the Zoology Department at the University of Kassel. Picture credit: Uni Kassel

The fossil is not larger than a millimetre and for its small size has a relatively large mouth around which four pairs of cone-shaped apertures are arrayed. The authors see these cones as openings into the oral cavity; the creature apparently had no anus. Presumably it expelled seawater and excreted waste through these cone-shaped openings. The animals lived on the seafloor. The researchers found 45 well-preserved fossil specimens in sedimentary rock at the Kuanchuanpu deposits in the Southern Chinese province of Shaanxi. They have given the newly discovered creature the name Saccorhytus coronarius.

The deuterostomes are a branch of animals that includes all mammals and thus also humans, as well as fish, amphibians, reptiles and birds. During the Ediacaran Period (ca. 541–635 million years ago), the deuterostomes split from the protostomes . In general, deuterostomes (in Greek: mouth second) share the characteristic that in an early embryonic stage the blastopore develops into the anus and the mouth develops elsewhere later. For protostomes, to which insects belong for example, this developmental sequence is reversed. So far, no fossils from the initial phase of deuterostome evolution had been discovered. This gap has now been closed with the discovery of these specimens.

"Our discovery casts a new light on the mysterious early history of deuterostomes," comments Dr. Ou. It makes it possible to draw new conclusions about some bilaterian characters. "The absence of an anus and the ventral position of the mouth in these animals suggest that the anus developed independently in a later phase of evolution and it first occurred after the separation of protostomes and deuterostomes."

Since July 2016, Dr. Qiang Ou, 39, has been a Humboldt Fellow in the Zoology Department at the University of Kassel. In the group of authors who wrote the just published paper, he performed the phylogenetic analysis, evaluating for example the anatomical characteristics of the discovered fossil.  Some part of his work took place in Kassel.

Prof. Dr. Georg Mayer, Dr. Ou's host at the Zoology Department of the University of Kassel, is very pleased about this important research achievement. "Qiang is a wonderful gain for our department and university. His success is a confirmation of our efforts to promote the international networking of our department."


The paper, "Meiofaunal deuterostomes from the basal Cambrian of Shaanxi (China)" has appeared in Nature on the 30th of January 2017.  Authors: Jian Han, Simon Conway Morris, Qiang Ou, Degan Shu & Hai Huang. The paper is available online at: http://www.nature.com/nature/journal/vaop/ncurrent/full/nature21072.html#videos

This is a report and a short video about the discovery in the New York Times: http://www.nytimes.com/2017/01/30/science/this-prehistoric-human-ancestor-was-all-mouth.html?_r=0

Here also is report on the discovery that appeared in The Independent: http://www.independent.co.uk/news/science/humanity-evolved-sea-creatures-large-mouth-no-anus-sccorhytus-millions-year-ago-micro-fossils-china-a7552611.html


Contact:
Sebastian Mense
University of Kassel
Communications, Press and Public Relations
Tel.: +49 561 804-1961
Email: presse@uni-kassel.de
www.uni-kassel.de