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Solving an unsolved problem: The egg was first

Max Toepper, Lorenz Dehn

Evangelisches Klinikum Bethel (EvKB), University Clinic of Psychiatry and Psychotherapy Bethel, Research Division, Remterweg 69-71, 33617 Bielefeld, Germany


Received 20.04.2023, accepted 28.11.2023, published 14.01.2024

Objective: To examine which came first, the chicken or the egg.
Design: Observational study, cross-sectional.
Setting: Online surveys.
Population: 216 participants from the general population including 194 novices and 22 experts.
Main outcome measures: Percentage of novices and experts who decided that the chicken was first, or the egg respectively. Certainty of both groups that their decision was right. Group differences regarding these variables. Effect of sex, age, and education.
Results: Results revealed that both experts and novices share the opinion that the egg came first. Experts were more certain than novices that their decision was right. In the group of novices, the level of certainty was associated with higher age and male sex.
Conclusions: Due to the opinion of both novices and experts, the egg came first, but certainly, experts are more confident that their opinion is right. 
Keywords: chicken; hen; egg; first; cause; consequence


Although it may not seem obvious at first glance, domestic chickens (Gallus gallus domesticus) and their eggs certainly play an interesting as important role in medicine. For instance, the effects of consumable chicken products and egg substances on human health are repeatedly studied and discussed in the medical literature [1-3]. Hot chicken soup, for example, seems to have a positive effect not only on the speed of nasal mucus velocity [4], but also on well-being and cognitive functions [5,6]. Moreover, the chicken offers unique biological characteristics to be an important scientific model for basic and applied medical research [7-9]. From time to time, parts of eaten chickens enter inappropriate locations within the digestive tract and thus lead to (rather unusual) challenges in gastroenterology or emergency medicine [10-12]. The role of the egg in medicine is undoubted as well. More than 90 % of influenza vaccine worldwide is produced with the help of about 500 million eggs by injecting virus particles into the eggs’ protein. Vaccine against yellow fever is obtained with eggs as well, although the World Health Organization (WHO) is searching for alternatives.

Since the beginning of humankind or since the beginning of chicken farming at the latest, there is another unanswered question that is driving scientists crazy worldwide: What came first, the chicken or the egg? Although the chicken was already domesticated in India since around 3200 B.C. [13], no convincing empirical evidence was provided for either one or the other. In 2006, the Guardian reported about a debate between different experts including a philosopher, a geneticist and a chicken farmer [14]. The debate was conducted promoting the launch of Chicken Little on DVD and resulted in the unanimous conclusion that it must have been the egg that came first. The experts explained their decision by arguing that a chicken egg must be defined as an egg with a chicken inside, even if this egg was laid by another animal. Consequently, the first chicken must have come from a chicken egg, even though this egg did not come from a chicken. Further evidence for the egg was provided by a German newspaper article [15] reporting that eggs would have existed since more than 300 million years ago, whereas the first chicken representatives appeared about 50 million years ago. In fact, domestic chickens as we know them appeared only a few thousand years ago. Another evolutionary approach yielded similar results: The first bird being called a chicken developed in the egg by a mixture and mutation of parental genes. Importantly, the new species did not only exist after having left the egg, but already before within the egg. Hence, it was argued that the egg must have been first. Other biologists rather take the view that there was neither a first chicken nor a first chicken egg, because there was no first animal that possessed the skills to create the following generations by utilizing an egg. From a religious perspective, it was God who created all kinds of animals and thus also the chicken. After sexual activities with the first cock (i.e. rooster), the hen laid the first egg, which then spawned the first little chicken (not to be confused with Chicken Little). Hence, the chicken must have been first.

Noteworthy, empirical evidence is sparse. Chicken et al. reported lipid-protein interactions [16], while Egg et al. linked oxygen to time [17]. Unfortunately, both studies could not explain the complex relationship between chicken and egg, because they had nothing to do with this topic. Although a PubMed literature research for “chicken and/or egg” in the title resulted in more than a hundred studies, it remains completely unclear which came first, the chicken or the egg. Moreover, it is unclear whether novices and experts share the same opinion and how certain they are that their opinion is right.


Study population

In an observational cross-sectional study (ChEgg – Pro: Chicken-Egg-Problem), we therefore examined 194 novices and 22 experts. Sample characteristics are displayed in Table 1. There were no exclusion criteria except that an online survey had to be completed. Novices were recruited via social media and mailing lists. Experts included members of different poultry breeders associations and egg-processing companies who were directly contacted via email. In the respective messages, we provided a link to the online survey. Participants gave informed consent. All procedures were in accordance with the declaration of Helsinki and approved by the Ethics Committee of Bielefeld University; and of course, no animals (e.g. chickens) were harmed.

Table 1: Sample characteristics

Patient and public involvement

Patients and public were not involved in the process of planning and performing the current research, neither chickens or eggs.

Study protocol and data collection

Both novices and experts participated in an anonymous online survey. The online survey was presented using the software toolbox Qualtrics. At the beginning of the online survey, participants were informed about objectives, procedures and data protection. After that, participants gave their informed consent and provided some demographic information (sex, age, and years of education). In particular, the survey required to decide which came first, the chicken or the egg by clicking the respective box on the screen. Moreover, participants were asked to estimate the correctness of their decision (certainty in %) by placing a bar on a continuous scale between 0 and 100. The two measures described were the primary outcomes of the study. Mean duration for completing the survey was 2.4 (± 8.7) minutes with a range between 24 seconds and 2.1 hours.

Statistical analyses

Initial quality check of the variable characteristics using graphical inspection and the Kolmogorov-Smirnov-Test (p < .05) did not indicate a normal distribution for any of the metric variables. Therefore, two-sample Mann-Whitney-U-tests and Chi2-tests were used for group comparisons between novices and experts. Moreover, Spearman correlations and partial rank correlations were utilized to describe the relations between the variables for both groups separately. Since inclusion criteria required finishing the online survey, there were no missing data. Data were analyzed with IBM SPSS Statistics 25.0 (SPSS Inc.). All levels of significance were α ≤ 0.05 and tests were two-tailed.


Study population

Initially, 730 novices and 114 experts were contacted. Of these 844 participants, 206 novices and 24 experts started the online survey. 12 novices and 2 experts did not complete the survey. Eventually, data of 194 novices and 22 experts were analyzed. Although there were proportionally more men in the expert group, both groups did not statistically differ regarding sex distribution at p <0.05 (male vs. female: Chi2  = 3.65, p  = .068). However, experts were older than novices (U = 627.0, Z  =  − 5.43, p  < 0.001) and had less years of school education (U = 1458.0, Z =  − 2.62, p  = 0.008).

Egg versus chicken

Results showed that 105 novices (54.1 %) thought that the egg came first, whereas 89 novices (45.9 %) thought that the hen came first. In the expert group, 15 subjects voted for the egg (68.2 %) and 7 subjects for the hen (31.8 %). However, the group difference between novices and experts was not significant at p < 0.05 (Chi2 = 1.58, p = 0.260). Neither in the whole sample nor within the novice and expert subgroups, egg or chicken voters significantly differed in terms of gender, age, or years of school (all p > .05).

Certainty of decision

Novices estimated the correctness of their decision at 58.7 % with a range between 0 and 100 %, whereas experts estimated the correctness of their decision at 90.9 % with a range between 50 and 100%. About 55 % of the experts (n = 12), but only 11 % of the novices (n = 21) were 100 % sure that their answer was right. Overall, experts showed a higher level of certainty than novices (U = 666.0, Z = -5.32, p < 0.001, see Table 1). However, for both novices (U = 4474.0, Z = -.51, p  = .609) and experts (U = 52.0, Z = -.04, p  = .988), there were no significant differences in certainty ratings between egg and chicken voters.

In the group of novices, higher age (rs = 0.21, p = 0.003) and male sex (rs = 0.26, p <0.001) were correlated with higher certainty that the decision was correct. Moreover, male sex was correlated with age (rs = 0.41, p < 0.001) indicating more male participants in the higher age range. Controlled for age, male sex still correlated with higher certainty that the decision was correct (rp = 0.20, p = 0.006). Controlled for sex, the correlation between higher age and higher certainty tended to be significant (rp = 0.12, p = 0.10). In the group of experts, no significant correlations were found.


The results of the current work provide empirical evidence that both experts and novices share the opinion that the egg came first. Thereby, experts were more certain than novices that their opinion was right. In the group of novices, the level of certainty was associated with higher age and male sex. The question whether chicken or egg came first has interested scientists and philosophers since the Greeks, because it is basically a question about the origin of life [18]. Extending the classical question of which of both came first, some theoretical work has proposed even more precise interpretive and conceptual issues, such as “Which came first – the chicken, or a thing laid by a bird that can later be called a bona fide chicken egg, even if it was not one originally?” ([19], p. 3). Moreover, from a philosophical point of view, there are proponents of both the chicken and the egg (e.g. [20] vs. [21]), and a particularly accurate differentiation concerns the conceptual subtlety between “chicken-produced” and “chicken-producing” eggs [22]. However, whereas biological and evolutionary approaches rather represent the opinion that the egg was first, religious approaches take the opposite view. Unfortunately, empirical evidence is sparse.

Closing this empirical gap, our results based on the data of 216 participants support the view that the egg came first and the chicken was second. In fact, the majority of both novices and experts voted for the egg. These findings clearly contradict the results of Alice S. Kaswell who empirically determined that the chicken came first [23]. In her experiment, she mailed a chicken and an egg, each in its own separate packaging, and kept careful track of when each shipment was sent from a post office in Cambridge, Massachusetts, and when it arrived at its intended destination in New York City. In this study, the chicken was faster which is not surprising because chickens can fly even without support whereas eggs cannot. Further limiting the generalizability of these results, the sample size was pretty small (n = 2). In fact, whereas in the past it was more common to rely on single field experiments (Kaswell, see above) or small expert commissions (Guardian, see above), modern (medical) science appears to base research results on ever increasing sample sizes.

Although not statistically significant, the percentage of decisions for the egg tended to be higher in the expert group than in the group of novices. Moreover, experts were more certain than novices that their opinion was right. These results might underpin the expertise of the experts. On the other hand, however, it cannot be ruled out that the experts are just more convinced than novices that their opinion is right. The level of certainty in the expert group was 90.9 % in average and ranged between 50 and 100 %. Hence, even experts who were not certain about their decision provided a certainty of at least 50 %. By contrast, novices rated their level of certainty to only 58.7% in average with a range between 0 and 100 %. Thereby, 41 out of 194 novices (21 %) rated their level of certainty under 50%, which raises the question whether these ratings should not count for the chicken instead. In other words: Given that we have to decide between chicken and egg and we decide for the egg with a certainty of only 49 % or less, do we then think the opposite? However, beside expertise there seem to be other factors that are associated with the level of certainty. In the group of novices, the level of certainty was positively correlated with higher age and male sex. Regarding age, it might be that older people were more certain than younger people, because the time when they arrived on earth is closer to the time when chicken and egg arrived. The result that male subjects were more certain that their opinion is right may certainly lead to challenging discussions at breakfast tables worldwide ;)

The current work was based on online surveys among the human beings and not amongst the chickens or eggs because of the developed communication channels with the former. However, the validity of online surveys to answer questions from the area of natural philosophy is a matter of debate, because surveys reflect collective agreements rather than the definite truth. Nevertheless, there are modern interdisciplinary approaches of experimental philosophy targeting philosophical questions with empirical methods that are more akin to psychology.

Overall, findings on this topic are inconsistent. Probably, humans may have just forgotten across centuries whether chicken or egg came first due to a collective episodic memory dysfunction. Definitely, more studies including larger samples are needed to be able to draw valid conclusions about the complex mechanisms between chicken and egg. While the question of the earliest documented chicken in a particular country still seems to play a very contemporary scientific role [24], future research projects should shed more light on the size of the chicken coop, for example. Additional questions particularly involve the color of the first egg (i.e. white or brown) and the name of the first hen. And what about the cock? When came the cock? The answers to all of these questions may help to solve other important problems as well, such as the question of what came first, hunger or thirst.


Competing Interests: All authors have completed the ICMJE uniform disclosure form at and declare: no support from any organization for the submitted work; no financial relationships with any organizations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work. Noteworthy, the authors did not receive any pay-offs from chickens or farmers. However, one of the authors confessed that he surprisingly found more chocolate eggs on the last easter than in the years before.

Funding: There was no funding source for this study.

Ethical approval: This research has the ethical approval of the Ethics Committee of Bielefeld University (2022-047).
Transparency statement: All authors affirm that the manuscript is an honest, accurate, and transparent account of the study being reported; that no important aspects of the study have been omitted; and that any discrepancies from the study as originally planned (and, if relevant, registered) have been explained.

Data sharing: Anonymized trial data are available from the corresponding author.

Author contributions: All authors accept full responsibility for the work and/or the conduct of the study, had access to the data, and controlled the decision to publish. All listed authors meet authorship criteria and no others meeting the criteria have been omitted. LD and MT had the idea while having scrambled eggs for breakfast in the office. LD and MT designed the online survey. LD, however, made a short break to serve a hot chicken soup. LD analyzed the data while MT counted the eggs needed for vaccines in the last year (500.001.473). LD and MT wrote the article, which made lots of fun. For the whole time, LD and MT knew that the egg was first, but they told nobody.

Read more:

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