Evolution Icon Evolution

Trace Fossil Experiments Put Pressure on Cambrian Explosion


Take a look at side-by-side photos in the middle of an article posted by NASA’s Astrobiology Magazine. They look identical, but the ones on the left are fossils, and the ones on the right were made in the lab by shuffling around microbial mats. The title of the article suggests a setback for evolutionists: “First Signs of Animal Life on Earth May Be from Microbes.”

To muffle the Cambrian explosion, scientists have searched for clues to the existence of complex animals in the Precambrian. The so-called “trace fossils” dating back to the Ediacaran (600 million years ago) provided some hope. Maybe they were made by ancestral trilobites or worms, the thinking was. Reporter Amanda Doyle explains:

Scientists are attempting to put a date on the earliest lifeforms in the kingdom of Animalia, but without an actual cast of a body they’ve had to rely on the credibility of “trace” fossils to show signs of an animal’s presence in the form of footprints, scratches, feeding marks or burrows. Some scientists claim to have found trace fossils made by animals more than a billion years ago, raising controversy over whether animal life could have existed this early. There are also trace fossils from the Ediacaran Period and soft bodied animals were known to exist during this period, so understanding the tracks they made is important for studying the early animals.

Giulio Mariotti, an oceanographer from Louisiana State University, and colleagues, examined supposed animal trace fossils from the Ediacaran Period, and found that it is possible that some of them could be microbial in origin. The results, which were recently published in a paper entitled “Microbial Origin of Early Animal Trace Fossils” in the Journal of Sedimentary Research, raise questions about the reliability of trace fossils as evidence for early animal life. [Emphasis added.]

The research, funded by the Exobiology & Evolutionary Biology division of NASA’s Astrobiology Program, does not rule out animals as the cause of the trace fossils. The similarities to lab experiments with microbial mats moved with low energy waves, however, are striking. The researchers not only reproduced trackways but also the grooves, pits, and “wrinkle structures” in the fossils, interpreted to be microbial mats. Simple alterations in the wave velocity produced both.

This research does not necessarily mean that all early trace fossils were caused by microbial aggregates, however it does put forward a plausible alternative explanation for those that occur alongside wrinkle structures. Therefore, possible trace fossils from the Ediacaran period or earlier should be looked upon with skepticism until it is possible to rule out microbial aggregates as a cause of the grooves and pits in the rock.

The article claims that later trace fossils after the Ediacaran become more complex and three-dimensional. Giulio Mariotti, oceanographer from Louisiana State, comments that “It is easier to challenge old trails because they have less ancillary information associated with them.” His team will be running more experiments to try to distinguish between trace fossils created by microbes and others possibly created by animals.

The abstract of the paper in the Journal of Sedimentary Research, though, doesn’t hold out much hope that the fossils are from complex animals. Shaking up microbial mats is capable of creating a wide variety of structures:

Elongate surface trails that abound in late Ediacaran and early Paleozoic sandstone and siltstone are often attributed to early animals. These trails commonly exist on the same beds as wrinkle structures (millimeter- to centimeter-size ridges and pits that are interpreted as evidence of the former presence of microbial mats). Here we show that interactions between oscillatory flow and centimetric microbial aggregates produce elongate trails on the surface of a sediment bed. Trails left by moving microbial aggregates share a number of characteristics with some presumed trace fossils of the earliest animals: elevated edges, zig-zag patterns, smooth curves, reversals, intersections with other trails, series of pits, and paths that terminate abruptly and restart nearby. Under the same flow conditions, millimetric microbial aggregates generate wrinkle structures. Thus, the interaction between flow and microbial aggregates on a sediment bed can produce a number of structures that are commonly interpreted as evidence of early animal locomotion.

The burden of proof appears to be on the evolutionists. To claim that complex animal body plans predated the Cambrian explosion, they will have to distinguish between their trace fossils and the structures Mariotti’s team was able to generate with microbes. The microbial explanation seems preferable, given that “Microbial mats were widespread in the Precambrian, the period before animal life became extremely common and diverse.”

The findings make sense if the explosion was real. Many Precambrian strata were perfectly capable of preserving even soft tissues of adult animals, as shown by the preservation of delicate sponge embryos. Where are they?

“Absence of evidence is not evidence of absence, some scientists like to say.” That’s fine. But if you want to make a case for a long fuse leading up to the explosive appearance of 18 or more animal phyla, sooner or later you need to show evidence. Three hoped-for classes of evidence have now been called into question by evolutionists themselves: the molecular clock, Ediacaran fossil connections, and now trace fossils. After 157 years of fossil hunting since Darwin, the reality of the explosion remains the best supported conclusion from the available evidence.

Photo: Trace fossil made by a trilobite, by Wilson44691 (Own work) [Public domain], via Wikimedia Commons.