"The deepest sin against the human mind is to believe things without evidence." -Thomas Huxley
As echoed by Thomas Huxley, believing in claims without evidence is a grave error as it undermines the foundation of rational inquiry. Accordingly, I would like to invite you to engage in thoughtful introspection regarding your personal beliefs. Reflect on whether these convictions are substantiated by evidence, or if they actually stem from the influence of tradition, familial and social circles, or perhaps from figures of authority. However, before reflecting on that matter, we must ask ourselves, "what counts as evidence?" Some may say that personal recounts and experiences counts as evidence. Some may say that a high number of people believing in a claim counts as evidence for the claim being true. Some may say tradition is evidence, because millions of people in the past believed in a phenomenon. The answer to all of those statements is: no, they do not count as evidence and in fact, they are junk evidence. Why is that so? In this blog post, I will use the term 'junk evidence' to define evidence that fail to be considered valid. As for evidence that are deemed to be valid, I will define them as 'scientific evidence'.
This image was created with the assistance of DALL·E 3.
But first... Falsifiability
However, before we begin, it is absolutely important to note that we must first consider if a claim, or theory, is falsifiable (i.e., able to be proven wrong)—read my blog post "What is a Scientific Theory?" to find out more on vulnerability to falsification. Briefly, if a claim or theory is not open to falsification, it is considered by science to be an invalid claim immediately. Thus, it makes no sense to even look at the evidence for it, since the evidence itself would not be falsifiable as well. I will use the example of the "Fire-breathing dragon" from the late esteemed astronomer, Carl Sagan, to illustrate what unfalsifiable claims look like.
The subsequent excerpt is extracted from Sagan's (1996) work, titled "The Demon-Haunted World: Science as a Candle in the Dark."
"A fire-breathing dragon lives in my garage" Suppose (I'm following a group therapy approach by the psychologist Richard Franklin) I seriously make such an assertion to you. Surely you'd want to check it out, see for yourself. There have been innumerable stories of dragons over the centuries, but no real evidence. What an opportunity! "Show me," you say. I lead you to my garage. You look inside and see a ladder, empty paint cans, an old tricycle — but no dragon. "Where's the dragon?" you ask. "Oh, she's right here," I reply, waving vaguely. "I neglected to mention that she's an invisible dragon." You propose spreading flour on the floor of the garage to capture the dragon's footprints. "Good idea," I say, "but this dragon floats in the air." Then [you propose using] an infrared sensor to detect the invisible fire. "Good idea, but the invisible fire is also heatless." [Then you propose using] spray-paint [on the] dragon [to] make her visible. "Good idea, but she's an incorporeal dragon and the paint won't stick." And so on. I counter every physical test you propose with a special explanation of why it won't work. Now, what's the difference between an invisible, incorporeal, floating dragon who spits heatless fire and no dragon at all? If there's no way to disprove my contention, no conceivable experiment that would count against it, what does it mean to say that my dragon exists? -Sagan (1996)
Carl Sagan went on to state that failing to falsify the hypothesis of the fire-breathing dragon, is not the same as proving its truth, because it is a claim that is unfalsifiable in the first place. Claims that can't be tested or are unfalsifiable, lack any kind of worth, even if the claims inspire or evoke a sense of wonder and excitement.
As such, only when claims are falsifiable—like all scientific theories are—then we can begin scrutinising the evidence supporting them. If they are not falsifiable, rationality tells one that these claims are not worth any value, since the proponents of the the claims would simply twist and turn them to fit any observation of reality.
Image source: "Carl Sagan." Encyclopædia Britannica. Encyclopædia Britannica, https://www.britannica.com/biography/Carl-Sagan#/media/1/516196/267240. Accessed 6 December 2023.
Biggest Enemy: Personal Recounts, Beliefs, and Experiences
To my surprise, the most common forms of unfalsifiable evidence that the public brings up to defend their claims, are personal recounts, beliefs, and experiences. This is due to their seductive allure, as they appeal to one's emotions of fear, wonder, excitement, and awe, in order to convince them that something is true. Ever seen the eyes of children sparkle when they talk about the tooth fairy visiting them the previous night? or when they exclaim "Santa came down the chimney last night and gave me a bicycle!" Are those evidences of the tooth fairy and Santa Claus? Surely not... But why?
Firstly, personal recounts, beliefs, and experiences are subjective, not observable, and therefore, not vulnerable to falsification. While we may not be able to refute or deny the claimant's personal pyschological experiences—I can't deny a child's excitement when they believed the tooth fairy visited them during their sleep—they certainly do not count as evidence to support any objective claim about the physical world.
Furthermore, even if we were to ignore its inability to be falsified, how does a belief in something even counts as evidence about a physical phenomenon? This is an example of a non sequitr fallacy (i.e., a conclusion that does not logically follow from its preceding premise). In other words, personal beliefs in a physical phenomenon are not evidence of the physical phenomenon being true, because the flow of reasoning makes no logical sense at all.
I'll demonstrate another non sequitr fallacy —having a high number of people believing in something also does not make that thing true—sadly, many seem to agree that they do. It's like saying since Disney Parks are everywhere in the world with billions of kids believing in the characters, so they must exist! Also, consider this, before Copernicus discovered heliocentrism in 1543, all of humankind used to believe that the sun moved around the Earth. So, ask yourself, was the sun orbiting the Earth back then because everyone believed in that 500 years ago? Did they then swapped places once humans learnt that it's actually the other way round? Of course not. Similarly, millions of kids believing in the existence of the tooth fairy does not make the tooth fairy's existence true. Millions of adults believing in ghosts and spirits, or any form of superstition, does not make them true. If the spirits are invisible and undetectable through any physical tests, then Carl Sagan's response would be most fitting, "Now, what's the difference between an invisible, incorporeal, floating [spirit], and no spirit at all?"
I ask that you reflect on yourself, what claims do you believe just because others, like your family and friends, believe in it. Have you scrutised the evidence yourself for these claims? Are these evidences empirical, positive, reproducible and public? (we'll get to these terms later) In essence, beliefs are not evidence, and truths do not care about beliefs.
This image was created with the assistance of DALL·E 3.
Science is not Based on Beliefs
Before I move on to what a scientific evidence entails, there's one more important point I have to make.
In my view, and that of many others, the term 'believe' or 'beliefs' should be omitted from discussions about scientific theories across all literature. This exclusion is crucial to avoid widespread misconceptions. Scientists do not subscribe to beliefs. They accept. No physicist believes in Einstein's general theory of relativity and Atomic theory; they accept them. No biologist or geneticist believe in Darwin's theory of evolution and the existence of DNA; they accept them. No microbiologist believes in germ theory of diseases; they accept it. No astronomer or geographer believe in a spherical Earth; they accept it. On what basis do they accept it? The answer is scientific evidence.
The Hallmarks of Science
Accordingly, apart from falsifiability, which is the first firewall criterion I expanded on in the earlier paragraphs, scientific evidence must qualify for all the following four criteria:
(1) Empirical: must be objective and observable, not figments of the imagination or based on personal recounts or experiences, as they are subjective
(2) Positive: must directly support the claim
(3) Reproducible: must be reproducible (i.e., repeatable) by others
(4) Public: must be made available to public, including the detailed steps taken to acquire them. This allows the public to scrutise the evidence and reproduce it
Any evidence that do not meet any of the above criteria, is considered to be 'junk evidence'.
Examples of Scientific Evidence used to Support a Claim
Claim: Modern humans evolved from ancient apes in Africa (Almécija et al., 2021; Langergraber et al., 2012; Sarich & Wilson, 1967).
I selected 3 pieces of scientific evidence, which are vulnerable to falsification, that supports Claim A
Scientific Evidence 1 (Molecular Biology and Genetics): DNA analysis shows that DNA of humans are, out of all species, most similar to chimpanzees' (around 98.5%), followed by other primates such as bonobos and gorillas (Britten, 2002; Ebersberger et al., 2002).
Empirical: Evidence is based on direct observation and experimentation. Scientists analyse the genes from both species, examining the similarities and differences in their DNA sequences through empirical methods such as DNA sequencing and analysis.
Positive: Directly supports the first part of the claim (humans evolved from ancient apes).
Reproducible and Public: Different research groups, using independent laboratories and methodologies, can conduct similar analyses and arrive at comparable results. The results that the DNA of humans are most simlilar to chimpanzees, followed by other primates, has been reproduced by countless studies from the 1980s till today. The evidence obtained from DNA comparisons are made public through rigorous peer review and dissemination within the scientific community. Scientists publish their research in reputable journals such as, PubMed, Science, Nature, and Royal Society Open Science, providing an avenue for researchers, or anyone who is competent, from all around the world to critically evaluate, replicate, or question the results.
Scientific Evidence 2 (Paleontology, Biogeography and Geology): Fossil findings of bipedal early hominins, like Sahelanthropus tchadensis, Ardipithecus, and Australopithecus, are predominantly located in East and North Africa, and nowhere else (Britannica, 2021). Note that there were no instances where modern human fossils have been found lower than the rock layers where the fossils of Homo erectus, Australopithecus, and Ardipethecus, were found. This suggests that modern humans came into existence only after these species have done so. The fossil record, along with genetic analysis of fossils, also documents how Homo sapiens (i.e., modern humans) migrated out of Africa into Europe, Asia, and the rest of the world, around 300,000 years ago (Andrews, 2019). Radiometric dating methods were used to date the age of fossils.
Empirical: Based on direct observation of fossils. Based on testing using methods such as radiometric dating.
Positive: Directly supports the claim (ancient apes and modern humans lived in africa, and modern humans migrated from Africa to the rest of the world).
Reproducible and Public: Details regarding the precise locations and stratigraphic layers containing hominin fossils have been disclosed, facilitating the potential for anyone to conduct excavations at the site and uncover similar fossils. This transparency enables the independent reproduction of results by anyone from the public or scientific community. Furthermore, researchers globally can independently apply radiometric dating methods on current and future fossils, ensuring the verification and replication of the dates assigned to the fossils. Evidence is also publicised via scientific journals for public scrutiny and replication of studies.
Scientific Evidence 3 (Paleontology and Morphology): Comparative and functional morphology of hominin fossils and modern humans show cranial expansion (i.e., increased in skull size), reduction in jaw protrusion and canine size, as well as transition from quadrupedalism to bipedalism (Pontzer, 2012). Modern humans also have tailbones (coccyx) and wisdom tooth, supporting that ancestors of modern humans used to have tails (because apes evolved from monkeys), and larger jaws.
Anatomical comparisons of apes, early hominins, Australopithecus, Homo erectus, and humans.
Source: Pontzer, H. (2012) Overview of Hominin Evolution. Nature Education Knowledge 3(10):8
Note. A male chimpanzee skull is shown as an example of modern apes. Early hominins and Australopithecus retained ape-size brains. Bipedal walking evolved very early in the hominin lineage, but Ardipithecus (and possibly other early hominins) retained a grasping foot that may have diminished bipedal efficiency. Reduced canine size also evolved early in the hominin lineage, although early hominin canines were larger and more pointed than those of later hominins. Molar size increased with Australopithecus but later is reduced in Homo (note: premolars are not shown in this schematic). Arboreal locomotion, as indicated by the presence of long arms, curved fingers and toes, and other forelimb features, was common throughout much of the hominin lineage.
Empirical: Based on direct observation of fossils and their homology.
Positive: Directly supports the claim (humans evolved from ancient apes in africa).
Reproducible and Public: Fossils of hominins are in museums and labaratories for anyone to inspect the similarities with modern humans—skeletal model of humans can be found in any primary school classroom. This allows reproducibility of evidence as future fossils discovered will be used to check against to validate the evidence. Fossil findings of Ardipithecus, Australopithecus, and Homo Erectus have been reproduced by numerous studies since their initial discoveries in the late 19th and early 20th centuries.. Evidence is also publicised via scientific journals for public scrutiny and replication of studies.
Taken as a whole, independent lines of scientific evidence (Evidence 1, 2, and 3), from various disciplines such as molecular biology, genetics, paleontology, geology, biogeography, as well as comparative and functional morphology, support the claim that modern humans evolved from ancient apes in Africa. With that, I hope these examples give you a better understanding of what counts as scientific evidence. Below is a chart, taken from Encyclopædia Britannica. (n.d.), showing the various types of hominin fossils that have been found.
Inductive Inference from Observations
Some would argue that because we did not see humans evolving from apes directly, means we can't say for certain. The argument that because we cannot directly observe a phenomenon, therefore it cannot be certain, is a misconception that overlooks the robustness of scientific inference and evidence. Using that argument, does that mean theory of plate tectonics is false, since we did not see Pangea splitting apart 200 million years ago? Does it mean that the Earth does not orbit the sun, because if you didn't know, nobody has ever directly observed the Earth moving around the Sun even till today. Does it mean that if no one directly observes a murderer killing someone, it's impossible for the court to convict the murderer and he should get away scot-free? Of course not.
Read more about the scientific method, which covers inductive inferences over here.
"Inductive inference is the only process known to us by which essentially new knowledge comes into the world" -Ronald Aylmer Fisher
Therefore, for those who buy into the argument that we need to directly observe a phenomenon to confirm it, it would be prudent for them to relenquish their acceptance of our Earth orbiting the sun, since nobody directly observed it. They should also make sure to take out the trash in front of mom's line of sight, otherwise there's no way to confirm that they did that, even if everyone observed that the trash is empty, that their hands are stained, and that they were standing next to the trash chute.
Conclusion
With that, I have emphasised the necessity for a claim to be falsifiable to be even worth any value. I've also highlighted how beliefs are unfalsifiable and therefore, belong to the pile of junk evidence along with personal recounts or experiences. In addition, beliefs do not make a claim true and is a perfect example of the non sequitr fallacy. I also shared my rationale as to why scientific discussions should drop the use of the word "believe" when it comes to scientific theories, as they are only accepted based on evidence, and never on beliefs. I also emphasised that if a claim passes the first test of being vulnerable to falsification, we must then scrutise the evidence that supports the claim. These evidence should fufill all the criteria of being empirical, positive, reproducible, and public—I used an example showing how 3 independent lines of scientific evidence support human evolution and migration out of Africa. Lastly, i demonstrated that science uses inductive inferences from indirect or direct observations to formulate theories and claims, which are foundational to the building of new knowledge in the world. Most importantly, I hope you've reflected on your personal beliefs and determine if they are based on proper scientific evidence, or not. If it's the latter, I would like to remind you that it's never too late to change your mind on outdated beliefs, in light of new evidence or new knowledge. To me, it is a sign of a healthy mind that is willing to learn from new information, and it calls for celebration when one lets go of their preconceived notions about reality, when confronted with evidence from reality. Clinging on to preconceived notions and refusing to look at evidence that challenges them is a one way ticket to denouncing learning and rationality, while embracing dogmatism and irrationality.
"The willingness to change one’s mind in the light of new evidence is a sign of rationality not weakness." - Stuart Sutherland
Reference
Andrews, P. (2019). Last common ancestor of apes and humans: Morphology and environment. Folia Primatologica, 91(2), 122–148. https://doi.org/10.1159/000501557
Almécija, S., Hammond, A. S., Thompson, N. E., Pugh, K. D., Moyà-Solà, S., & Alba, D. M. (2021). Fossil apes and human evolution. Science, 372(6542), eabb4363. https://doi.org/10.1126/science.abb4363
Britannica, T. Editors of Encyclopaedia (2021). human evolution summary. Encyclopedia Britannica. https://www.britannica.com/summary/human-evolution
Britten, R. (2002). Divergence between samples of chimpanzee and human dna sequences is 5%, counting indels. Proceedings of the National Academy of Sciences, 99(21), 13633-13635. https://doi.org/10.1073/pnas.172510699
Ebersberger, I., Metzler, D., Schwarz, C., & Pääbo, S. (2002). Genomewide comparison of dna sequences between humans and chimpanzees. The American Journal of Human Genetics, 70(6), 1490–1497. https://doi.org/10.1086/340787
Encyclopædia Britannica. (n.d.). Human evolutionary pathways [Image]. Encyclopædia Britannica. https://www.britannica.com/topic/Homo-sapiens#/media/1/1350865/45440 Accessed December 18, 2023.
Langergraber, K. E., Prüfer, K., Rowney, C., Boesch, C., Crockford, C., Fawcett, K., Inoue, E., Inoue-Muruyama, M., Mitani, J. C., Muller, M. N., Robbins, M. M., Schubert, G., Stoinski, T. S., Viola, B., Watts, D., Wittig, R. M., Wrangham, R. W., Zuberbühler, K., Pääbo, S., & Vigilant, L. (2012). Generation times in wild chimpanzees and gorillas suggest earlier divergence times in great ape and human evolution. Proceedings of the National Academy of Sciences, 109(39), 15716–15721. https://doi.org/10.1073/pnas.1211740109
Pontzer, H. (2012) Overview of Hominin Evolution. Nature Education Knowledge3(10):8
Sagan, C. (1996). The dragon in my garage. The demon-haunted world: Science as a candle in the dark.
Sarich, V. M., & Wilson, A. C. (1967). Immunological time scale for hominid evolution. Science, 158(3805), 1200–1203. https://doi.org/10.1126/science.158.3805.1200 Tuttle, R. Howard (2023). human evolution. Encyclopedia Britannica. https://www.britannica.com/science/human-evolution
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