Where's the Evolution?

 

The horseshoe crab is a common example of a "living fossil" or "Lazarus taxa", 

a modern organism that demonstrates very little divergence from its ancestors in the fossil record.

Introduction

"Living fossils" (also known as "Lazarus taxa" or "stabilomorphs") are modern organisms that have maintained consistent form over an indefinitely long period, with their ancestors in the fossil record closely resembling their modern-day anatomical makeup. (Garrod, 2023) A famous example is that of the Coelacanth, a lobe-finned fish that disappeared from the fossil record around 65-80 million years ago, only to be found alive and well in the coastal waters of southeast Africa and Southeast Asia during the early 20th century. (Smithsonian, n.d.) By resembling their ancestors so closely, they have led some to question the universality of evolutionary processes - both Genesis Apologetics and Creation Ministries International have cited living fossils as evidence against evolution in their Questions for Evolutionists material, joining other mainstream creationist groups like Answers in Genesis and the Institute for Creation Research in asking how evolution can leave some organisms "unchanged" while others diversify widely. The objection is summed up in the question "Where is the evolution?" How can some organisms stay "the same" for seeming millions of years?

Evolutionary Stasis

The main issue with this objection is thinking in terms of a dichotomy, assuming that if evolutionary processes can change organisms wildly over very long periods, then they cannot leave them unchanged for long periods. This way of thinking about evolution isn't entirely accurate, because evolution selects for traits that make organisms more likely to survive in a given environment, as we've covered elsewhere on this site. So, if an organism is very well suited to survive in a stable environment, then it won't face any pressure to adapt and its traits will continue to be selected by the environment. This phenomenon is called "evolutionary stasis", when a species exhibits little significant evolutionary change over long periods, maintaining a consistent morphology. (Lidgard & Hopkins, 2015) 

Imagine you have a favorite recipe that you love to cook - something classic that's been in your family for generations. The dish is already loved by everyone, and very little needs to be done to improve or alter it. Other dishes, you may want to experiment with until you find something everyone likes - substitute this or that ingredient, modify temperature or cooking time, add this or that seasoning, etc. Evolutionary stasis is like the family recipe, where nothing much is needed to enhance what's going on - the "recipe" for a living fossil works for organisms well-suited for stable environments. Just as there's no need to alter a recipe everyone already loves, there's no environmental pressure for these organisms to change since they fit well and have their survival needs met. The "recipe" for organisms that are in greater competition for resources or in changing or unstable environments are like the ones that you might experiment with. Evolution is all about how organisms respond to their environment, not about change or lack of change. Thinking of evolution as a dichotomy, where it can either only change things or leave them unchanged, is like thinking you can only ever cook meals a certain way or constantly change each one you cook. You're able to stick with recipes that work or adapt and experiment on them based on needs and preferences, just like evolutionary processes are.

Creation Ministries International doesn't recognize this, as in the 2006 article on living fossils titled 'Evolutionary stasis': double-speak and propaganda, they state:

"By any definition, evolution involves change in form or function, but stasis means essentially no change. Therefore, 'evolutionary stasis' is, at best, totally meaningless...This type of loose thinking has become commonplace among people who speculate about evolutionary origins. Scientists and laypeople are generally unaware of the way in which a person's belief system colors his/her view of the world. This is why it is so important to emphasize having the "correct glasses" on when dealing with origins science." (Bell, 2006)

However, Bell doesn't acknowledge two key realities in his reductionist assessment of living fossils. The first is the claim that evolutionary stasis means that "no change" has occurred in an organism's history, which is not true. 

Living Fossils: Identical to their ancestors?

Despite retaining similar, well-working physiological traits possessed by their ancestors, living fossils aren't identical to their ancestors and have diverged in significant ways. For example, another CMI piece from 2013 claimed that 230 million-year-old gall mites preserved in amber were identical to modern gall mites that had undergone "no evolutionary change", stating that:

"...for the duration of the claimed 230 million years, there have been no significant changes in these organisms. This is the classic 'living fossil' syndrome, highlighting the problem of 'evolutionary stasis'." (Cessna, 2013)

However, when biology professor Joel Duff reviewed the article that Creation Ministries International wrote, he found that the author had seemingly not read the paper discussing the mites, because the original researchers found that despite the fossil's similar appearance to their descendants:

"They cannot be assigned to any of the three extant families, partly due to inadequate classification in this superfamily, as well as to some unusual attributes of the fossils. The very divergent body structure of the fossils indicates they are distantly related, which is further supported by Triasacarus lacking integrated feeding appendages." (Schmidt et al., 2012, emphasis added)

 Duff continues in addressing the claim that the ancient and modern mites being discussed are identical:

"Notice the "unusual attributes" "divergent body structures" and "distantly related" in this?...These are similar enough that we can identify them as gall mites but are they the same as ones alive today? Absolutely not! They are so different that they cannot be identified as to what family of gall mites they belong...gall mites are well adapted for their niche and evolutionary theory predicts that 200 million years from now there could well be organisms that look very similar (but not absolutely identical especially in their genomes) to today's gall mites...Nothing in evolutionary theory says that organisms are bound to evolve into things that don't look like their ancestors." (Duff, 2013)

Various living fossils claimed to have "not evolved" actually show adaptive morphologies that distinguish them from their ancestors. A few examples of several popular living fossils would include:

• Coelacanth - As mentioned in the introduction, the Coelacanth was thought to have gone extinct tens of millions of years ago but was rediscovered in the 1930s. Despite common beliefs about modern coelacanths being identical to their fossil ancestors, Sam Hardman of Ecologica notes that: "...the most widely held belief about coelacanths is that..they look exactly the same now as they did millions of years ago. This belief is mistaken. No fossils are known for either species of surviving coelacanth or even for members of its genus, Latimeria. This suggests that the scientists responsible for classifying the fossil and living species consider the morphological differences so great (that) they should be placed in widely separate groups. In fact, there are significant differences in the body shape and structure of modern and extinct coelacanth species. These include changes in the number of vertebral arches and substantial differences in skull morphology. The swim bladder has also changed from being filled with oil the extinct genus Macropoma, to being ossified in modern species..." (Hardman, 2013)

• Horseshoe Crab - Dating back 450 million years, horseshoe crabs have a simple and effective physiological and anatomical makeup that is well-suited to their environment. To quote Dr. Russell Bicknell and Dr. Nicolas Campione, who conducted one of the most in-depth studies on horseshoe crab evolution published in 2022, "Over the past four years, we have studied the fossil record, examining the shape, size, and development of 44 species of horseshoe crabs dating back to the Carboniferous period...While we found that the way in which a horseshoe crab grows has remained relatively constant since that period, we realized that the shape and size has actually changed considerably since at least the Carboniferous." (Bicknell et al., 2022) (UNE, 2022) They and other researchers noted wide diversity in morphology, size, general design, number and function of legs and gills of horseshoe crabs despite enduring features seen today. (Gershon, 2012)

• Ginkgo Biloba - This tree species has existed for over 200 million years, with modern ginkgos resembling those from the Jurassic period but not being entirely identical. Peter Crane notes in his evolutionary biography of ginkgo trees comparing fossilized Ginkgo yimaensis and other extinct ginkgos to living Ginkgo biloba: "Its leaves were deeply divided, more like the sucker shoots and seedling leaves of living ginkgo rather than the mature foliage, and the seeds were borne on individual stalks rather than sessile as in living G. biloba. However, the fossil genera Yimaia and Karkenia were more distinct. Yamia had leaves that were very deeply divided into narrow digitate lobes, and seeds that were borne in clusters. In Karkenia, the seeds were massed together in cone-like aggregations and each was borne on a distinct reflexed stalk...increasing paleobotanical evidence shows that the ginkgo lineage also included plants with simple, strap-shaped, leaves, and reproductive structures very different from those of the living species." (Crane, 2018)

• The Wollemi Pine - The Wollemi pine is frequently labeled a "living fossil", even though clear evidence of its development is absent from the fossil record. The genus it occupies (Wollemia) bears strong resemblance to two other extant genera (Araucaria and Agathis) in the same family (Araucariaceae), with Wollemia demonstrating intermediate characteristics between Agathis and Araucaria. (Seyfullah et al., 2023) However, a comparison between extant Wollemi and Cretaceous Wollemi fossils demonstrates a variety of diversity in leaf arrangement, shape, cuticular features, cone scales, etc. (Chambers et al., 1998)

The genetic mechanisms of evolutionary stasis

In regards to living fossils, the Institute for Creation Research echoes Bell's sentiments, stating that the "...most straightforward explanation for why the living form looks so much like the fossilized one is that instead of eons of evolution having taken place, both were created recently." This type of out-of-pocket dismissal doesn't acknowledge the unique genetic processes that govern evolutionary stasis that aren't observed in other organisms. A 2021 ISME paper (Becraft et al.) looked at the bacteria Candidatus Desulforudis audaxviator (CDA), which was first found in water deep underground in South African gold mines. The bacteria has been found in many other deep underground places with various samples taken from around the world demonstrating nearly identical DNA despite the populations studied having been separated for potentially millions of years. The researchers found that this was due to the bacteria possessing a very efficient manner of copying and repairing their DNA, a mechanism not observed in other microbes. (Becraft et al., 2021) If all microbes were created at the same time, why are these more efficient at copying their DNA than others? 

This uniqueness is also seen in living fossils above the macroscopic. For example, a study published this year in Evolution compared the genomic exons of two living fossils, gars and sturgeons, to a dataset of nearly 500 vertebrates, and found that genetic change/mutation in the living fossils occurred much slower than in the other organisms used in the comparison. (Brownstein et al., 2024) These results echo previous work conducted by researchers in 2023 that found that over several generations, Anolis lizards maintained longer morphological stability despite normal/expected levels of genetic evolution occurring between parent and offspring (i.e., in the short-term, evolutionary development was occurring, but in the long-term the previous selections were "canceled" out, leading to long-term stability). (Arnold, 2024) (Peake, 2023) (Stroud et al., 2023) If assuming all organisms were created at the same time and living fossils are just developing naturally like all other organisms, how would that explain unique genetic qualities observed in living fossils but not in other organisms? What's more, if organisms remaining the exact same for millions of years is supposed to speak against evolutionary processes, how are organisms that have changed significantly between their first appearance in the fossil record and the present supposed to be explained? How does the ICR view account for whales, whose earliest ancestors (like Indohyus and Pakicetus) were semi-aquatic and had four limbs, whose descendants like Ambulocetus and Dorudon were distinct not only from their ancestors but also from their later descendants in the form of modern cetaceans? (Thewissen et al., 2009) How would it account for the diversification of birds, who first appeared among the Maniraptora of the Jurassic and whose descendants (Avialae) are not at all morphologically identical to their ancestors? (Chiappe, 2009) If the ICR's position were correct, then we would expect all organisms alive today to be very similar to their fossil ancestors - but we don't see that.

Conclusion

Asking "Where's the evolution" when it comes to living fossils seems like a great "gotcha" question if you assume that evolution can only constantly change organisms, but this reflects a serious misunderstanding of what evolution is and how it operates. The idea that these organisms have remained unchanged since their creation, alongside all other forms of life, fails to account for the distinct genetic traits unique to living fossils. These organisms don't support the idea that all organisms were created at the same time, since certain traits of living fossils are not found in other organisms, and other extant organisms have undergone significant diversification since they first appeared in the fossil record. Understanding the unique evolutionary pathways of living fossils is essential since it highlights the complexity/variability of evolutionary processes across different species and environments, and allows for more productive conversations between advocates of evolutionary models and those who are opposed to them.

References

Arnold, C. (2024, January 2) Evolution: Fast or Slow? Lizards Help Resolve a Paradox. Quanta Magazine.

Becraft, E. D., Lau Vetter, M. C. Y., Bezuidt, O. K. I., Brown, J. M., Labonte, J. M., Kauneckaite-Griguole, K., Salkauskaite, R., Alzbutas, G., Sackett, J. D., Kruger, B. R., Kadnikov, V., van Heerden, E., Moser, D., Ravin, N., Onstott, T., Stepanauskas, R. (2021) Evolutionary stasis of a deep subsurface microbial lineage. The ISME Journal, 15, 2830-2842.

Bell, P. (2006) 'Evolutionary stasis': double-speak and propaganda. Creation, 28(2), 38-40.

Bicknell, R. D., Kimmig, J., Budd, G. E., Legg, D. A., Bader, K. S., Haug, C., Kaiser, D., Laibl, L., Tashman, J. N., Campione, N. E. (2022) Habitat and developmental constraints drove 330 million years of horseshoe crab evolution. Biological Journal of the Linnean Society, 136(1), 155-172.

Brownstein, C. D., MacGuigan, D. J., Kim, D., Orr, O., Yang, L., David, S. R., Keiser, B., Near, T. J. (2024) The genomic signatures of evolutionary stasis. Evolution, qpae028.

Cessna, S. (2013, May 16) Claimed 'oldest-ever' amber fossil - millions-of-years mighty mites? Creation Ministries International.

Chambers, T. C., Drinnan, A. N., McLoughlin, S. (1998) Some Morphological Features of Wollemi Pine (Wollemi nobilis: Araucariaceae) and Their Comparison to Cretaceous Plant Fossils. International Journal of Plant Sciences, 159(1).

Chiappe, L. M. (2009) Downsized Dinosaurs: The Evolutionary Transition to Modern Birds. Evolution: Education and Outreach, 2, 248-256.

Crane, P. R. (2018) An evolutionary and cultural biography of ginkgo. Plants, People, Planet, 1(1), 32-37.

Duff, R. J. (2013, May 16) NH Notes: Gall Mites in Amber Similar but Not the Same As Today. Naturalis Historia.

Gershon, E. (2012, September 10) In horseshoe crab history, legs come and go. Yale News.

Garrod, B. (2023, May 24) What is a living fossil? Discover Wildlife.

Hardman, S. (2013, August 24) Coelacanths are not living fossils. Ecologica.

Lidgard, S., Hopkins, M. (2015, August 31) Stasis. Oxford Bibliographies.

Peake, T. (2023, October 10) How Does Constant Evolution Keep Species Stable? NC State News.

Schmidt, A. R., Jancke, S., Lindquist, E. E., Ragazzi, E., Roghi, G., Nascimbene, P. C., Schmidt, K., Wappler, T., Grimaldi, D. A. (2012) Arthropods in amber from the Triassic Period. Proceedings of the National Academy of Sciences, 109(37), 14796-14801.

Seyfullah, L. J., Coiro, M., Hofmann, C. (2023) In situ pollen diversity in the relict conifer Wollemia nobilis. Review of Palaeobotany and Palynology, 309, 104816.

Smithsonian (n.d.) Coelacanth (Latimeria). National Museum of Natural History.

Stroud, J. T., Moore, M. P., Langerhans, R. B., Losos, J. B. (2023) Fluctuating selection maintains distinct species phenotypes in an ecological community in the wild. Proceedings of the National Academy of Sciences, 120(42), e2222071120.

Thewissen, J. G. M., Cooper, L. N., George, J. C., Bajpai, S. (2009) From Land to Water: the Origin of Whales, Dolphins, and Porpoises. Evolution: Education and Outreach, 2, 272-288.

University of New England (2022, January 31) UNE researchers uncover new patterns of horseshoe crab evolution.