Result #1

Honest signals need not be costly at the equilibrium not even under conflict of interest. We have shown this result in discrete and continuous models as well (Számadó, 1999; Lachmann et al., 2001).

Számadó, Sz. (1999) The Validity of the Handicap Principle in Discrete Action-Response games. Journal of Theoretical Biology, 198, 593-602.

Lachmann, M., Számadó, Sz. and Bergstrom, C.T. (2001) Cost and Conflict in Animal Signals and Human Language. Proc.Natl.Acad.Sci.USA 28, 13189-13194.

Result #2

Honesty is maintained by condition dependent trade-offs. We have shown this result both in a general model of signalling and by experimentally (Számadó et al., 2022, 2023).

Számadó, S., Samu, F., & Takács, K. (2022). Condition-dependent trade-offs maintain honest signalling. Royal Society Open Science, 9(10), 220335.

Számadó, S., Zachar, I., Czégel, D., & Penn, D. J. (2023). Honesty in signalling games is maintained by trade-offs rather than costs. BMC biology, 21(1), 1-16.

Result #3

What is important for honesty is a the potential cost of cheating; deception is prevented when this potential (marginal) cost is higher than the potential (marginal) benefit for would be cheaters (Számadó, 1999; Lachmann et al., 2001).

Számadó, Sz. (1999) The Validity of the Handicap Principle in Discrete Action-Response games. Journal of Theoretical Biology, 198, 593-602.

Lachmann, M., Számadó, Sz. and Bergstrom, C.T. (2001) Cost and Conflict in Animal Signals and Human Language. Proc.Natl.Acad.Sci.USA 28, 13189-13194.

Result #4

Honest individuals need not pay a cost (see previous point), in fact they can enjoy a benefit at the equilibrium (Számadó et al., 2023).

Számadó, S., Zachar, I., Czégel, D., & Penn, D. J. (2023). Honesty in signalling games is maintained by trade-offs rather than costs. BMC biology, 21(1), 1-16.

Result #5

Deception can be part of a stable polymorphic equilibrium in models of conflict (symmetric games). The frequency of cheaters can be very high (Számadó, 2000; Számadó, 2017).

Számadó, Sz. (2000) Cheating as a Mixed Strategy in a Simple Model of Aggressive Communication. Animal Behaviour, 59, 221-230.

Számadó, S. (2017). When honesty and cheating pay off: the evolution of honest and dishonest equilibria in a conventional signalling game. BMC Evolutionary Biology, 17(1), 270.

Result #6

Threat displays are not handicaps, they are beneficial for honest signallers, they prepare them to fight (Számadó, 2003).

Számadó, Sz. (2003) Threat displays are not handicaps. Journal of Theoretical Biology 221, 327-348

Result #7

The honesty of threat displays are maintained by proximity risk, i.e. by the risk of the opponent to launch a successful attack. Honesty declines with increasing distance between signallers. Threat displays are expected to be honest at close range, a mixed honest/bluffing strategy can persist at midrange, bluffing will replace honesty at a large distance (Számadó, 2008).

Számadó, Sz. (2008) How threat displays work: species-specific fighting techniques, weaponry and proximity risk. Animal Behaviour, 76, 1455-1463.

Result #8

Repeated interactions can promote honesty in dominance displays (Számadó, 2011).

Számadó, Sz. (2011) Long-term commitment promotes honest status signalling. Animal Behaviour. 82 295-302.

Result #9

Attention seeking displays, that do not provide information about the quality of the signaller, only help to locate them, can be evolutionarily stable (Számadó, 2015).

Számadó, Sz. (2015) Attention Seeking Displays. PLOS one 10(8): e0135379.

Result #10

I have shown that Zahavi’s major claims are incorrect, thus the Handicap Principle can be rejected. Furthermore I reviewed biological mechanisms that can maintain cheap yet honest signals at the equilibrium (Számadó, 2011)

Számadó, Sz. (2011) The cost of honesty and the fallacy of the handicap principle. Anim.Behav. 81, 3-10.

Result #11

We have investigated how Zahavi’s handicap principle, an erroneous idea, became popular and rose to prominence in biology (Penn & Számadó, 2020).

Penn, DJ & Számadó, Sz (2020) The Handicap Principle: how an erroneous hypothesis became a scientific principle. Biological Reviews 95 (1), 267-290.

Result #1

We formulated a set of criteria (Számadó & Szathmáry, 2006) to evaluate the alternative selective scenarios that were proposed in the literature to explain the evolution of early human language. The set of criteria I as follows: (i) honesty, (ii) groundedness, (iii) power of generalization and (iv) uniqueness.

Számadó, Sz. & Szathmáry, E. (2006) Selective scenarios for the emergence of natural language. Trends Ecol. Evol. 21(10), 555-561.

Result #2

We have shown (Számadó & Szathmáry, 2006) that none of the proposed theories fits all four criteria, that is none of them can provide a logically coherent explanation for the evolution of early human language.

Számadó, Sz. & Szathmáry, E. (2006) Selective scenarios for the emergence of natural language. Trends Ecol. Evol. 21(10), 555-561.

Result #3

I have developed my own theory that fits the above criteria (Számadó, 2010). I proposed that early language evolved in the context of pre-hunt communication. I argue that early language evolution can be seen as a two-step process: at first indexical and iconic signs evolved to coordinate recruitment for the hunt; then later, in the second stage, the complexity of this communication system increased to coordinate group-hunting effort including division of labour. I provide a review of the fossil record and show that the available evidence is fully compatible with the theory.

I derived several predictions from the pre-hunt communication model (Számadó, 2010):
1. H. erectus possessed a communication system suitable for recruitment and for the coordination of the hunt, this should be reflected in the organization of the H. erectus brain.
2. H. erectus is the first hominid species that is expected to be frequently associated with middle- and large-sized mammalian fossils showing cut marks referring to active meat acquisition.
3. H. erectus is expected to be in resource competition with other savannah-dwelling big-game hunters (and bonecrackers).
4. As H. erectus must have had a communication system suitable for recruitment and pre-hunt coordination, all the descendants of H. erectus, including H. heidelbergensis, H. neanderthalis, and of course H. sapiens must have had a communication system at least of that level of complexity.
5. Assuming that skulls with horns were the first indexical signs that started the evolution of human language, one would expect this to be reflected in the fossil record.
6. Assuming, on one hand that drawing originated in the context of pre-hunt communication to facilitate coordination of the group’s hunting effort, on the other that cultural systems have inertia, one would expect the earliest pieces of art to depict big game that can be hunted only by a coordinated group effort.
7. The model also predicts the lack of pre-hunting communication that serves to coordinate future action or prey type in other group hunting species.
8. There should be no genetically inherited mental models of hunting in humans—not even in contemporary hunters. It follows that even contemporary hunters have to learn both the use of weapons and the tactics of the hunt.

Számadó, Sz. (2011) Pre-Hunt Communication Provides Context for the Evolution of Early Human Language. Biological Theory. 5, 366-382.

Result #1

We have investigated the effect of dispersal and neighbourhood size in spatial games of cooperation, prisoner’s dilemma and snowdrift games (Számadó et al., 2008). We have shown:
1. Spatial correlations are always beneficial to cooperators in both the PD and SD games.
2. It is the limited neighbourhood and not spatial correlations that decreases the frequency of cooperators in spatially explicit models of populations.

Számadó, Sz., Szalai, F. and Scheuring, I. (2008) The effect of dispersal and neighbourhood in games of cooperation. Journal of Theoretical Biology, 253, 221-227.

Result #2

We have investigated the effect of multilevel selection on threshold public goods games (Boza & Számadó, 2010). We have shown that:
1. There are polymorphic equilibria in Threshold PGGs.
2. Multi-level selection does not select for the most cooperators per group but selects those close to the optimum number of cooperators in terms of the Threshold PGG.
3. Cooperation can be stable in Threshold PGG, even when the proportion of so called free riders is high in the population.

Boza, G. Számadó, Sz. (2010) Beneficial laggards: multilevel selection, cooperative polymorphism and division of labour in Threshold Public Good Games. BMC Evolutionary Biology. 10, 336.

Result #3

We show with a novel demographic model that the biological rule “During your reproductive period, give some of your resources to your post-fertile parents” will spread even if the cost of support given to post-fertile grandmothers considerably decreases the demographic parameters of fertile parents but radically increases the survival rate of grandchildren. The teaching of vital cultural content is likely to have been critical in making grandparental service valuable. We name this the Fifth Rule, after the Fifth Commandment that codifies such behaviors in Christianity.

Garay, J., Számadó, S., Varga, Z., & Szathmary, E. (2018). Caring for parents: an evolutionary rationale. BMC Biology, 16(1), 53.

Result #4

We show that regulated farming of prey bacteria and delayed digestion can facilitate the establishment of stable endosymbiosis if prey-rich and prey-poor periods alternate. Stable endosymbiosis emerges without assuming any initial metabolic benefit provided by the engulfed partner, in a wide range of parameters, despite that during good periods farming is costly. Our approach lends support to the appearance of mitochondria before any metabolic coupling has emerged, but after the evolution of primitive phagocytosis by the urkaryote.

Zachar, I., Szilágyi, A., Számadó, Sz., & Szathmáry, E. (2018). Farming the mitochondrial ancestor as a model of endosymbiotic establishment by natural selection. Proceedings of the National Academy of Sciences, 115(7), E1504-E1510.