The American horseshoe crab, Limulus polyphemus
Here is a article that Creationists can use to make fools of themselves with by showing they don't understand the subject about which they consider themselves to be leading experts.
It is about the so-called 'living fossils' - species that have remained superficially unchanged for tens, even hundreds of millions of years. I say superficially because there is no way to know how much evolution has occurred because we don't have samples of the species' DNA from millions of years ago, so we only have the physical appearance to go by and a great deal of evolution happens in genes that control the physiology or soft tissue and birdsstructures, not in the hard body-parts that more easily fossilise.
The other thing that Creationists make fools of themselves with is their naive assumption that there must be some rule in the Theory of Evolution which says species evolve at a more or less constant rate, so remaining unchanged means the TOE is wrong, conveniently forgetting that the handful of 'living fossils' are dwarfed by the millions of species with evidence of evolutionary change in just a few million years, including all living and extinct mammals and birds.
In the following article, the first thing to note is that all the examples of 'living fossils' are marine creatures, most of which inhabit the deep ocean floor or even buried in it. Away from mid-ocean ridges and the subduction zones around the edges of land masses, this is one of the most stable environments on Earth.
Since the primary driver of evolution is environmental change and maladaptation, producing opportunities for environmental selectors to select for or against genetic variations, a stable environment and/or near perfect adaptation means there will be little or no pressure to evolve. This is not a fault with the theory but a confirmation of it, in that it predicts that environmental change will drive evolutionary change, so it follows that environmental stability will result in little or no evolutionary change.
Here then is a sample of these 'living fossils' in an article from The Conversation by Alice Clement, Research Associate in the College of Science and Engineering, Flinders University, Australia. It is reprinted here under a Creative Commons license, reformatted for stylistic consistency. The original article can be read here:
From coelacanths to crinoids: these 9 ‘living fossils’ haven’t changed in millions of years
Shutterstock
Alice Clement, Flinders University
We see evolution all around us, constantly, in every living thing. Yet in the deep oceans we find a number of "living fossils" reminiscent of creatures from prehistoric times.
In his 1859 book On the Origin of Species, esteemed naturalist Charles Darwin coined the term "living fossil" to describe living organisms that appeared unchanged from their extinct fossil relatives. The term has since been used to describe long-enduring lineages, relict populations, groups with low diversity, and groups with DNA that has hardly changed in millions of years.
The marine depths seem to be a good place for "living fossils", with cartilaginous fish such as sharks and rays generally being 2-4 times more evolutionarily distinct than land animals. In other words, while every species is unique, these species are particularly unlike their closest relatives.
Let’s take a look at some of these relics from the past.
1. Coelacanth
Coelacanths are fish that live deep off the coasts of Africa and Indonesia. They have unusually shaped paired body fins which they move alternatively, almost as if they’re “walking” underwater. Their lineage stretches back to the Devonian Period, at least 410 million years ago.
It was once thought coelacanths had gone extinct alongside (non-bird) dinosaurs about 70 million years ago, as they disappear from the fossil record around this time.
Allenypterus montanus, a fossil coelacanth fish from the Bear Gulch Limestone in Montana.
Credit: James St. John
So imagine the surprise when a living specimen was dredged up from the deep ocean in 1938! This fish became known as “Old Fourlegs” and was thought to be the direct fishy ancestor of all land animals (although we now know this isn’t strictly correct).
Today there are two living coelacanth species, known as Latimeria, which have basically remained unchanged over the past 100 million years.
2. Horseshoe crab
Horseshoe crabs are ancient creatures that first appeared at least 480 million years ago during the Ordovician Period and don’t appear to have changed much since. They are not crabs at all, but “chelicerates” and therefore more closely related to spiders and sea scorpions.
You can find Horseshoe crabs at Bowers Beach in Delaware.
Credit: Jeffrey
They also have strange blue blood, coloured that way due to a high copper content. Horseshoe crabs are harvested for their blood by the pharmaceutical industry since it has uses in biomedical testing.
Mesolimulus walchi is an extinct species of horseshoe crab.
Credit: Petr Hykš
3. Elephant shark
Similar to horseshoe crabs, “elephant shark” (Callorhinchus milii) is a misnomer. This species, also known as the Australian ghost shark, is not a shark at all. It’s a related type of cartilaginous fish known as a “chimaera” and belongs to a subclass called Holocephali which diverged from the shark lineage more than 450 million years ago.
These “plownose” chimaeras take their name from their bizarrely shaped snout and can be found living off the continental shelves of Australia and New Zealand.
Analysis of their genome has shown the species changes at a veritable snail’s pace. In fact, it has the slowest evolving genome of all vertebrates, with its DNA almost imperceptibly altered over hundreds of millions of years.
Callorhinchus milii is covered in distinct dark markings. It is commercially exploited in Australia.
Credit: Totti/Wikimedia
4. Nautilus
Nautilus live in the ‘pelagic’ zone, the large middle column of water that’s far from both the shore and ocean bottom.
Credit: PacificKlaus
Nautilus live in the open water in and around coral reefs in the Indo-Pacific Ocean. They’re hunted for their beautiful shells to make art and jewellery, but international trade is now regulated to protect them from over-exploitation.
Members of the Nautilidae family are known to have existed from the Late Triassic, and appear to have remained relatively unchanged for more than 200 million years. Darwin himself described these creatures as “living fossils”.
You’d struggle to tell an ancient Nautilus from a living one.
5. Goblin shark
The goblin shark (Mitsukurina owstoni) is a bizarre animal with a long, flat snout and toothy jaws that protrude in front of the face to catch unsuspecting prey. It’s a relatively rare deep-water shark living in all major oceans. With a face only a mother could love, it was described as “grotesque” when first encountered in 1910.
The goblin shark is the only living representative of its family, Mitsukurinidae, and is the most evolutionarily distinct shark we know of; its lineage stretches back some 125 million years.
Goblin sharks are rarely seen by humans.
Credit: Dianne Bray/Museum Victoria, CC BY
6. Mantis shrimp
Mantis shrimp, also called stomatopods, are distinctive crustaceans found in tropical and subtropical coastal waters around the world. They are fearsome marine carnivores known to deliver a dizzyingly fast and painful blow.
They also live a colourful life. During mating season they fluoresce (emit light) and have complex eyes to watch these displays. In fact, they have up to 16 colour receptors, whereas humans have just three.
Mantis shrimp have the fastest self-powered strike in the animal kingdom.
Credit: PiktourUK
The mantis shrimp lineage branched off from other crustaceans in the malacostraca class (such as crabs, lobsters and krill) during the Carboniferous, around 340 million years ago. So these fabulous, feisty critters have been flourishing for a long time. Today there are hundreds of species belonging to the suborder Unipeltata, which appeared some 190 million years ago.
7. Striped panray
A striped panray illustration from 1841.
Today, the striped panray lives in tropical waters in the eastern Atlantic (and possibly the Indian) ocean, and feeds on small invertebrates from the ocean floor. It belongs to the order Rhinopristiformes and is oviparous, meaning it gives birth to live young. It is listed as “vulnerable” by the International Union for Conservation of Nature.
8. Brachiopods
Brachiopods are shelly marine animals with long, fleshy stalks that live in burrows on the seafloor. They act as reef-building organisms, filter-feeding from the water around them. Brachiopods living today, such as Lingula, look more or less the same as their Cambrian counterparts from about 500 million years ago! They are considered the oldest known animal (genus) that still contains living representatives.
In The Origin of Species, Darwin noted “some of the most ancient […] animals as […] Nautilus, Lingula, etc., do not differ much from living species”. It’s these observations that led him to propose the term “living fossil”.
Brachiopods have hardly changed in hundreds of millions of years.
Credit: Rob Growler
9. Crinoids
Crinoids are known from at least the Devonian (359-419 million years ago) but may have existed as long ago as the Ordovician (more than 445 million). These marine animals, also known as “sea lilies”, once lived on the seafloor in a symbiotic relationship with corals. Corals grew off the stalks of crinoids to reach higher into the water column for better feeding opportunities.
A fossil crinoid species called Seirocrinus subangularis.
Credit: James St. John
Crinoids were thought to be extinct until 2021.
Credit: NOAA Ocean Exploration and Research
How do living fossils form?
While animals described as “living fossils” usually do continue to evolve, many of these changes are imperceptible to the human eye. To track how animals change over time, we look at molecular changes visible in the genes, or “morphological” changes to the physical form.
Internal (or molecular) drivers include genetic drift, which is the random change in the frequency of gene variants in a population over time. External forces include natural selection, in particular sexual selection, which lead to specific traits being inherited in a population over time.
All the marine animals in this list seem to be undergoing morphological stasis (slowing or stoppage). Some may have molecular stasis too. Their slowing rates of evolution are likely a result of the relatively stable environment underwater, particularly in the deep sea. These distant refuges are some of the least affected by direct human impacts and changes in weather and climate.
Then again, these animals are not immune. And if we’re not careful, we may lose some of these curious creatures forever.
A Latimeria (coelacanth) specimen at the South African Institute for Aquatic Biodiversity, and an excited human.
Alice Clement, Research Associate in the College of Science and Engineering, Flinders University
It's a mark of the ignorant gullibility of Creationists that they've been fooled into believing 'living fossils' prove the TOE is wrong when, in fact, they are solid evidence that it is right, to anyone who understands it.
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