Evolution of middle ear bones in mammals from jaw bones in reptiles?
Does the detailed evidence bear it out?
The reptilian jaw contains a number of bones not found in mammalian jaws. This includes the articular, a small bone on the back of the lower jaw; and the quadrate, a small bone on the upper jaw, at the base of the skull (figure 1). The articulation of the reptilian jaw is between these two bones, so it is called a quadro-articular jaw. At the front of the lower jaw there is the dentary. Mammalian jaws are very different, with only one bone one each side of the lower jaw, the dentary. This articulates with the squamosal in the upper jaw, hence dentary-squamosal jaw.
The reptilian middle ear contains just one bone, the columella, connecting the eardrum to the inner ear. In mammals, there are three middle ear bones, called the hammer (malleus), anvil (incus), and the stirrup (stapes), which take part in the transmission of sound toward the inner ear.
Evolutionists claim that the three reptile bones mentioned previously correspond to the three middle ear bones of mammals. Namely, the articular corresponds to the malleus, the quadrate to the incus, and the columella to the stapes. According to evolutionary theory, the articular and quadrate greatly shrank in size and changed in shape and somehow migrated into the middle ear, while the columella underwent no such process. Somehow these three bones were joined together to transmit sound from air to the watery environment of the inner ear.
However, as we noted in our previous article, there are two separate theories, which describe the origin of the malleus and the incus. According to the “dual-arch model”, the middle ear bones originate from two separate tissue areas called the first and second branchial arches, which are folds of tissue in the developing embryo’s neck area (figure 21, right). More precisely, a block of tissue in the first arch called Meckel’s cartilage is involved in this process. In contrast, the “classical view” says that just as in reptiles, the malleus and the incus both originate from the first branchial arch only, just like the articular and quadrate do in reptiles (figure 2, left). According to the classical view, mammals evolved from reptiles, since they inherit the origin of their middle ear bones from reptiles.
First round of arguments
From time to time we receive comments from different kinds of “village atheists”, who profess expertise in different areas of science.
For example, evolutionist James D. made the following claim in response to our web article on the alleged transition of jawbones in reptiles to the middle ear bones of mammals:
“Apparently staying slightly behind the data curve remains the YEC model. Re incus coming from the first arch:
Burford, Charlotte M., & Matthew J. Mason. 2016. “Early development of the malleus and incus in humans.” Journal of Anatomy 229 (December): 857-870.
Rodriguez-Vázquez, Jose Francisco, Masahito Yamamoto, Shinichi Abe, Yukio Katori, & Gen Murakami. 2018. “Development of the Human Incus With Special Reference to the Detachment From the Chondrocranium to be Transferred into the Middle Ear.” The Anatomical Record: Advances in Integrative Anatomy and Evolutionary Biology 301 (August): 1405-1415.”
Dr. Matthew Cserhati’s (CMI-US) first response:
It’s unprofessional just to present a reference list without any covering explanation. It also seems that you didn’t read your own references very carefully. Let me quote to you from the Burford article that you refer to:
"This ‘dual‐arch’ interpretation is commonly presented in otolaryngology2 textbooks, and it has been used by clinicians to explain the aetiology3 of certain congenital abnormalities4 of the human middle ear."
I don't understand why you single out young earth creationists, when the dual arch model is also held by many evolutionists. It is presented in textbooks, and even has a practical use in clinical diagnosis. Why this bias? Furthermore, according to Burford et al., "Although we cannot unambiguously reject the dual‐arch model of ossicular5 development, our observations, on balance, favour the classical interpretation." In other words, this is a contested issue, and further study is necessary to determine which model is correct. The paper also states that studies in mice show that not all of the malleus (excluding the goniale and orbicular apophysis) is derived exclusively from the first pharyngeal arch6. The article authors say that visual identification of first and second arch boundaries in embryos is a difficult task.
Even if the malleus and incus were both derived from the first pharyngeal arch, the third bone, the stapes isn't. Where are intermediate fossils which have only two bones on one side of the eardrum and the third on the other side?
Second round of arguments
James D. responded with a second argument:
“Thank you for your prompt reply. You're making the same mistake Duane Gish made decades ago, and which Hopson called him on in 1987: the bones moved as a unit, not one by one. Btw I have now source checked all your citations and your arguments will be covered in the new ‘The Rocks Were There’ book I am coauthoring, regarding the AiG Answers Book series and associated antievolutionism. Your misrepresentations of the data field qualify as blatant data suppression, especially the 2013 Anthwal paper, and the 2004 Tucker paper. I recommend everyone read those papers and compare their content with the claims you are making about them, especially in relation to the role of Bapx1 in jaw and ear development. … ”
Dr. Matthew Cserhati’s (CMI-US) second response:
We are not misrepresenting any author, or any kind of data. About the Bapx1 gene, let me cite the Tucker, 2004 article for you: “In fish, Bapx1 is responsible for the formation of the joint between the quadrate and articular … Contrary to expectations, [mouse] Bapx1 does not affect the articulation of the malleus and incus.” But even if Bapx1 does take part in the regulation of the middle ear bones, still, the question is, how do you explain how this one gene affects the formation of five other tissues (the forelimbs, hindlimbs, vertebral column, spleen and gut)?7 How likely do you think that the differential expression of this gene in at least one of these five tissues would not go together with an abnormality or imbalance of some sort?
The components of the middle ear (the bones, their muscles, and nerves as well as their genetic regulation) is an example of irreducible complexity. This means if a single bone is missing, then hearing is impossible. How can an animal hear which has two bones on one side of the ear, and one on the other? Let me ask you again, where are the missing links which have such a bone configuration? There are none. The development of each of the middle ear bones is controlled independently. According to Ralibar et al.8, a three-year old boy patient was found to be missing the incus in both ears, while the rest of the middle ear (including the malleus and the stapes) were both normal. After a partial ossicular replacement prosthesis (a bone replacement) was placed between the stapes and the malleus, his hearing improved. This means that the middle ear bones are formed individually. This paper comes from 2002, therefore since you overlooked it, your work represents poor scholarship.
Let me also mention the fact that the joints between the middle ear bones are synovial joints9 in mammals as opposed to fibrous joints10 between the quadrate and articular in reptiles. How do these joints change during evolution? The rewiring of these joints would involve a lot of changes in the genetic regulation and morphological structuring between reptiles and mammals.
The musculature of the middle ear bones in mammals is also different from that of reptiles. As you should know, two tendons, the tensor tympani and stapedius (figure 311) are responsible for the coil and recoil of the middle ear bones, and are attached to the malleus and the incus, respectively in the mammalian ear. These two muscles had to evolve in order to be able to move these two middle ear bones. In addition, since reptiles don’t have a tensor tympani, both the muscles and the nerves that innervate these two muscles had to evolve so that mammals could hear properly. In mammals, the fifth cranial nerve has branches that supply both the tensor tympani and also the medial pterygoid muscle, which is inserted into the middle part of the lower jaw. Whereas the tensor tympani produces minute, subconscious movements, the medial pterygoid muscle produces large-scale, controlled conscious movements. Now, imagine what would have happened during evolution if an originally reptilian fifth cranial nerve now partially innervates the newly evolved mammalian tensor tympani, which controls the movement of the newly evolved malleus. This way, hearing in mammals would initially be consciously controlled—clearly the evolutionary scenario of the middle ear bones forming in mammals is a made-up story.
Also, the structure of the mammalian stapes is different from that of the reptilian columella. How does the columella transform into the stapes? Furthermore, the reptilian quadrate and articular bones are jawbones, yet the malleus and incus fulfil roles in the transmission of sound to the inner ear. Besides new musculature and innervation, the genetic regulation of these genes must also have evolved between the two animal groups. How do they get rewired for two very different functions? Known mutations in the developmental process of the middle ear only lead to congenital abnormalities, and not the emergence of a new functional structure as required by evolution.
In humans, the section of Meckel’s cartilage which gives rise to the malleus and incus from the first branchial arch does not follow a trajectory towards becoming a quadrate and articular, which then becomes modified. On the contrary, these two bones take on their adult-sized form while they are still cartilage and only afterwards become bone. In other words, the embryological development of the quadrate and articular in reptiles is quite different from the development of the malleus and incus in mammals.
Some evolutionists such as James D. claim that there is evidence for a uniform development of the middle ear bones in both reptiles and mammals from the same tissue. Thus, they claim that mammals retained the development of the middle ear during embryonic development from reptiles. However, even according to our critic’s own sources, it is contested as to which precise tissue the middle bones come from in both animal groups.
The bones of the middle ear somehow had to appear on the other side of the eardrum if indeed reptiles evolved into mammals. These bones are regulated individually, so they do not necessarily move as a single unit. No theory exists as to how the regulation of the bones is rewired to transition from chewing to the transmission of sound to the inner ear. There is also no explanation as to how the musculature, innervation and the types of joints in these muscles also change between the reptile and the mammal stage. This is because the middle ear is an irreducibly complex designed system for transmitting sounds in mammals, whereas its function is entirely different in reptiles.
Once again, evolutionists must force the data to fit their pre-conceived ideas of the evolutionary transition from reptiles to mammals. A closer look shows that mammals are very different in structure from reptiles, because they had a separate origin. This shows that mammals were created separately from reptiles. Even when we look at the scientific details, evolution doesn’t measure up, but creation theory is vindicated.
References and notes
- Burford, C.M. and Mason, M.J., Early development of the malleus and incus in humans. J Anat. 229(6):857–870, 2016. Return to text.
- Otolaryngology is the medical study of the ears, nose and throat. Return to text.
- The aetiology is the anatomical description of a disease. Return to text.
- A birth defect involving structural or functional abnormalities during embryonic development. Return to text.
- Ossicular = pertaining to ossicles, literally ‘little bones’. Return to text.
- Pharyngeal arch = branchial arch, once associated with non-existent embryonic gill slits. Return to text.
- Chatterjee, S. et al., Gene expression profiles of Bapx1 expressing FACS sorted cells from wildtype and Bapx1-EGFP null mouse embryos, Genom Data. 5:103–105, 2015. Return to text.
- Rahbar, R., Neault, M.W., Kenna, M.A., Congenital absence of the incus bilaterally without other otologic anomalies: a new case report, Ear Nose Throat J. 81(4):274–6, 278, 2002. Return to text.
- A synovial joint is a joint between two bones (such as leg or arm bones), surrounded by a membrane and filled with fluid to ease movement of the joint. Return to text.
- A fibrous joint is a joint between two bones, which are connected by dense connective tissue, such as collagen. Joints between skull bones are examples of fibrous joints. Return to text.
- Bell, A. How do middle ear muscles protect the cochlea? Reconsideration of the intralabyrinthine pressure theory. J. Hearing Science 1(2):9–23, 2011. Return to text.