Evolutionary claims abound. As though scientists had just returned from a trip to the past after watching events unfold in real time, news blurbs report just so stories with a level of detail that current field observers would miss. This time the fossil discovery of sharks and shark eggs found up river from an ancient ocean sea shore spark the claim that sharks were migrating from rivers to oceans 310 million years ago. The amazing claim: Sharks were the first animals to migrate. The story is quoted here from January 15th New Scientist.
JAWS would be proud. The earliest animal known to migrate was a shark living about 310 million years ago. It lived in rivers but swam to the sea to breed.
Bandringa were primitive sharks with long spoon-shaped snouts that seem to have lived in freshwater and ocean habitats. That’s because they regularly migrated between the two, says Lauren Sallan of the University of Michigan in Ann Arbor.
Sallan’s team looked at Bandringa remains from three sites in Illinois. One was originally on the coast, the others were inland. At the coastal site, the oldest known shark nursery, they found the remains of young sharks … and eggs, and inland they found adult remains (Journal of Vertebrate Paleontology, doi.org/qt8). “That’s what lets us see the migration,” says Sallan.
It certainly seems to be the oldest evidence of a vertebrate migrating, says George Engelmann of the University of Nebraska at Omaha. But migration may go back further. “I could readily entertain the possibility that earlier vertebrates were making migrations between fresh water and salt,” he says.
In theory, the baby sharks might have been safe in fresh water, but Sallan suggests the sharks were
locked into an ancestral behaviour of breeding in the sea shallows to keep the young safe from predators.
Until recently scientists thought there had been two species of Bandringa, one that lived in fresh water and one that lived in the sea. But according to Lauren Sallan of the University of Michigan in Ann Arbor, there was only one species. The sharks migrated from their freshwater habitat to a saltwater nursery to reproduce.
Sallan says, “the three sites are segregated by age”. Juveniles and hatchlings were found alongside the eggs in the coastal site, while the bodies of adults were found inland. “That’s what lets us see the migration.” The coastal site is the oldest known example of a shark nursery.
In theory, the Bandringa‘s young might have been perfectly safe in their freshwater environment, but Sallan suggests that they were locked into their ancestors’ behaviour of breeding in the sea. Recent genetic evidence has shown that sharks return to where they were born to breed, and palaeontologists have long suspected that prehistoric sharks also migrated.
The Bandringa must have had sufficient memory capacity to return to the same location every time they bred. They would also have needed processes to control their salt levels as they moved from fresh water to saltwater and back again. Modern sharks do regulate their salt levels, but most are only ever in saltwater. “Because they made the switch from saltwater to fresh, theBandringa would have required a system to control their salinity levels in fresh water as well as saltwater,” says Sallan.
What remains quite amazing is that no mention is made of the fact that these fish were fossilized at all. First, these are not bony fish but cartilaginous animals making any other type of fossilization impossible except by catastrophic sedimentation. Second, the preservation of this find is incredibly detailed, capturing events which include baby sharks next to the eggs and baby sharks in a nursery of egg clutches. This preservation demands an almost instantaneous burial of still living and incubating sharks and eggs. Thirdly, the only reason that migration in fish would seem amazing is if one did not expect to see complicated behaviors in animals of an assumed ancient origin.
The real discovery should be that fish have always been fish and hence no evolution has occurred. There is nothing amazing about fish unless you are disappointed that the fossils do not show behaviors that would be considered more primitive (since at 310 million years fish were just being invented by evolution). Fourthly, the discovery of fossilized soft tissue is remarkable once again pointing to the rapidity of the fossilization event. Finally, not a whisper of the fact that if the oceans were 310 million years old they should not have been in the least bit salty back then. Saltiness is a product of the evaporation of water from the oceans. This leaves dissolved minerals and salts behind. In fact, the current saltiness of the oceans is a complete puzzle to oceanography since over 310 million years the oceans should have turned into a mineral sludge by now from all the materials that have been transported to them over such time.
There are no real indications of migration or any other unusual behavior to be found in these fossil sites. To pretend that as a scientist you know that the sharks lived up stream from oceans is make believe. To ignore as a scientist what you know about how these animals were killed and buried is unethical. To make assumptions about a salty ocean that you believe existed 310 million years ago is deliberately ignoring good science. To pretend that you have the power to interpret complex animal behavior from burial sites without first clarifying the dozens of assumptions that you must make on the nature of the fossil burial is meaningless. To arrive at conclusions about the intelligence, memory and behavioral habits of an animal that you know died catastrophically is absurd. Above all, to discover that fish have always been fish, that no evolution has occurred and yet summarize that the evolutionary significance to all of this is that you have found the first animal that migrated is so counter intuitive it makes the entire paper unscientific. In light of the assumption that the oceans were salty and to suppose these animals had more advanced means to manage the changes in salinity than sharks do today should impress anyone, especially a scientist, that de-evolution must be occurring.
The title should not read, “Shark claims title as earliest migrant” but “Amazing find proves fish have always been fish.”