Researchers have discovered an evolutionary link between ancient fish throats and the shoulder anatomy that allows humans to swing a golf club or reach high shelves.

Fish Fossil Revolution

The vertebrate shoulder is believed to have partially evolved from the gill arches of ancestral fishes, which were curved supports encircling the throat.

Fish Fossil Revolution

This analysis, reported in Nature, resolves the debate about the origin of the bones connecting our arms to our trunks, attributing it to both head tissues and lateral folds in ancient fish.

Fish Fossil Revolution

About 500 million years ago, vertebrates were jawless marine creatures with paired gill arches but no paired fins. Over time, fish called placoderms evolved, having jaws and a primitive "shoulder" supporting front fins. 2. 

Fish Fossil Revolution

Ichthyologists have long argued that jaws and the shoulder's precursor arose from an ancestor's most forward gill arch.

Fish Fossil Revolution

Others believed the pectoral girdle, which gave rise to the human shoulder, originated from lateral folds, representing trunk tissues.

Fish Fossil Revolution

Martin Brazeau, a paleontologist, examined placoderm fossils and discovered a divot at the back of the head, suggesting a connection to gill arches.

Fish Fossil Revolution

Placoderms likely evolved the pectoral girdle to enable better mouth opening and diverse feeding systems before supporting paired fins.

Fish Fossil Revolution

The divot, representing the sixth gill arch, serves as an anatomical landmark distinguishing head from trunk tissue, as observed in other extinct fish, the Osteostracans.

Fish Fossil Revolution