Were Leeches Originally Parasites?
Rare fossil leech
feasted not on blood but
on smaller marine creatures
by Jerry Bergman, PhD
A common argument against both Intelligent Design and Creationism is the claim that “an omniscient and benevolent deity would not have created human life that was very poorly designed.” However, many very good reasons exist for the design of this world.[1] A similar argument is “Why would God make pathogens that cause sickness and death?”[2]
One casualty of this argument is Canadian evangelist Charles Templeton who was so popular that up to 30,000 people a night would flock to hear him. In his heyday, he was more famous than his teammate, Billy Graham. Thousands professed to have found salvation in Christ through Templeton’s preaching. However, Templeton eventually became an atheist and authored a book titled Farewell to God: My Reasons for Rejecting the Christian Faith.[3] In this book, he writes that God’s “grand design also includes the creation of parasites: worms, fleas, ticks, lice … bacteria, viruses, and the aberrant cells that attack the body, the organs or brain, and the malignant cells that cause death and suffering.”[4]
Templeton gave two main reasons for his rejection of God. First, he had become convinced that evolution, not God, was responsible for the creation of humans. The second reason was the existence of pathogens and life-forms such as blood-sucking creatures, which he felt was not consistent with the existence of a Creator God. But are those sufficient reasons for rejecting the design evident throughout the world?
One explanation for these creatures given by creationists is that, originally, when created, these life-forms did not harm the creation. All this changed after the fall of Adam, when the world was cursed because of mankind’s sin. As a result, over subsequent generations, all of God’s original creation became corrupted through the accumulation of mutations in living organisms.
A Non-Bloodsucking Clitellata
Illustration from the UCR press release.
One newly discovered fossil was recently found in the Waukesha biota. This geological formation in Wisconsin is well-known for excellent preservation of the bodies of soft-tissue animals that usually decay before fossilization.
This fossil was of the parasite Clitellata, a major annelid worm clade comprising hirudineans (e.g., leeches). ‘Clitellata’ comes from the creature’s clitellum, a thickened, glandular ring of tissue found in certain segmented worms, including leeches. This glandular, non-segmented body region produces mucus to form a cocoon for its eggs. The researchers described the new fossil find as follows:
Due to their scant fossil record, the origins of clitellates, particularly Hirudinea, are poorly known. Here, we describe the first leech body fossil, Macromyzon siluricus, … from the Brandon Bridge Formation (Waukesha Lagerstätte). This fossil, which is preserved in exceptional detail, possesses several hirudinean soft-tissue synapomorphies–including a large sucker at the posterior end and sub-divided segments–and phylogenetic analyses resolve Macromyzon siluricus as a stem leech. Its age … predates molecular-clock-based estimates of hirudinidan origins by at least 200 million years. These findings suggest that the earliest true leeches were marine and that, contrary to prevailing hypotheses, were unlikely to have fed on vertebrate blood.[5]
Of interest is the response of the popular layperson’s view of this fossil finding, especially related to the conclusion that these Clitellata, in contrast to those existing today, did not feed on vertebrate blood. A press release from the University of California at Riverside concludes that these fossil leeches were unlikely to have fed on vertebrate blood, as is obvious in the title of the article, “Rare fossil reveals ancient leeches weren’t bloodsuckers.”[6] Jules Bernstein wrote in the press release that the “newly described fossil reveals that leeches are at least 200 million years older than scientists previously thought, and that their earliest ancestors may have feasted not on blood, but on smaller marine creatures.”[7]
A modern leech in the act of sucking the blood of its victim. Note how the neck is bent 90 degrees to attach to the victim’s skin. (Wikimedia Commons)
The leech specialists who examined the fossil find were convinced they had found a leech due to the tail sucker and the distinct body segmentation design, which is a combination that is only found in leeches. They have soft, muscular bodies that can lengthen and make a 90-degree turn to attach to their victim to suck its blood. (See illustration.)
Ignored in this study is the parasite-host relationship, a topic for future research.[8]
The Dating Problem
The fact that a single fossil discovery can push the record back by 200 million years—from 150–200 million years to 400 million years or more—demonstrates how uncertain and flexible evolutionary dating can be.
Other Problems
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The study of the fossil by leading Clitellata experts identified “a large tail sucker — a feature still found in modern leeches — along with a segmented, teardrop-shaped body. But one important feature isn’t found in this fossil: the forward sucker that many of today’s leeches use to pierce skin and draw blood.”[9]
According to University of California, Riverside paleontologist Karma Nanglu, the fossil “is the only body fossil we’ve ever found of this entire group.”[10] One fossil hardly allows firm conclusions to be drawn.
Questions that require answers include: “Was this a new species of Clitellata to add to the 680 identified species of leeches currently identified?” Stay tuned for more fossil discoveries, which may lend greater insight into history of these organisms. For now, the conclusion that the fossil find feasted not on blood but on smaller marine creatures, supports the alternative explanation of an accumulation of mutations since a very good creation.
References
[1] Howell, C., Designer Science: A History of Intelligent Design in America, New York University Press, New York, NY, p. 85, 2025.
If you’re looking for answers to the question, “Why did God create life-forms that have harmful side effects to other organisms?,” this is the book to read.
[2] Bergman, Jerry, Why Did God Create Viruses, Bacteria, and Other Pathogens, WestBow Division of Thomas Nelson and Zondervan, Bloomington, IN, 2023.
[3] Templeton, Charles, Farewell to God: My Reasons for Rejecting the Christian Faith, McClelland & Stewart, Toronto, Ontario, 1996.
[4] Templeton, 1996, p. 199.
[5] De Carlia, Danielle, et al., “The first leech body fossil predates estimated hirudinidan origins by 200 million years,” PALEONTOLOGY AND EVOLUTIONARY SCIENCE, https://peerj.com/articles/19962/, 2025; emphasis added.
[6] Bernstein, Jules, Rare fossil reveals ancient leeches weren’t bloodsuckers, https://news.ucr.edu/articles/2025/10/01/rare-fossil-reveals-ancient-leeches-werent-bloodsuckers, 2025.
[7] Bernstein, 2025.
[8] Silva, Luis, and Kayla King, “Ecology and evolution of virulence,” Current Biology,
https://www.cell.com/current-biology/fulltext/S0960-9822(25)01095-4, 22 September 2025.
[9] Bernstein, 2025.
[10] Bernstein, 2025.
Dr. Jerry Bergman has taught biology, genetics, chemistry, biochemistry, anthropology, geology, and microbiology for over 40 years at several colleges and universities including Bowling Green State University, Medical College of Ohio where he was a research associate in experimental pathology, and The University of Toledo. He is a graduate of the Medical College of Ohio, Wayne State University in Detroit, the University of Toledo, and Bowling Green State University. He has over 1,900 publications in 14 languages and 40 books and monographs. His books and textbooks that include chapters that he authored are in over 1,800 college libraries in 27 countries. So far over 80,000 copies of the 60 books and monographs that he has authored or co-authored are in print. For more articles by Dr Bergman, see his Author Profile.