The anthropic principle and its implications for biological evolution

“Carter's argument, the latest of the “Big Three,” is based on our ignorance about the characteristic temporal scales of biological evolution leading to emergence of intelligent observers [13,14].”

“Carter (1983) and Watson (2008) both argue that the strictly necessary steps for intelligent observerhood are probably very few, which implies that all the other evolutionary steps that have de facto shaped the character of the Earth, of human beings and of the Earth’s technosphere (for example the…”

“Finally, an argument made by Carter (1983) is based on the similarity between the biological evolutionary time scale here on Earth and the Sun’s evolutionary time scale.”

“], we include this discussion here anyway. 3.1. Would We Live in This Universe if the Hard Step Model Is True? The first hypothesis we consider is the hard step model, originally proposed in Reference [46]. Its tenet is that the emergence of intelligence requires a small number of very hard evolutionary innovations, ea…”

“It is rather unlikely that (say) * 50% are inhabited, because there is no reason for the scale of the environment needed for origin of life to be equal to the scale of a planet, even to order of magnitude (Carter, 1983; Lacki, 2016).”

“Bayes’ theorem gives an elegant way to express the concept of anthropic selection (Carter,1983; Waltham, 2007).”

“The step hypothesis has received attention from astrobiologists (Carter 1983; McKay 1996; Watson 2008).”

“Like the anthropic principle itself, the hard-steps model is applicable to humans and nonhuman entities alike—notably, extraterrestrial organisms ( 1 ), as well as any organism that has existed or will exist on Earth.”

“We focus here on what we expect to be a nested sequence of biosignatures, corresponding to the major evolutionary transitions that occur on Earth, as outlined in Carter (1983); Szathmáry & Smith (1995).”

“characteristic timescale for the emergence of intelligence is actually much greater than 4 Gyr (Carter, 1983; Watson, 2008).”

“The idea underlying the anthropic principle (Carter 1983; Leslie 1996; Bostrom 2002) is that to interpret what one observes when one emerges in the universe, one needs some idea of what might or might not be expected as far as one’s personal identity and situation in space and time are concerned.”

“One or more correlated steps might be highly improbable on a per-planet basis [36] (say P ∼ 10−n with n ≫ 24 so that the probability would be very low for any others within the observable universe of probably not more than 1024 planets).”

“nder the creation of agents who don’t yet know what reference class they are in. 5.3 The Doomsday argument Closely related to the Adam and Eve paradox, though discovered rst, is the Doomsday argument [CM83]. Based on SSA’s preference for ‘smaller’ universes, it implies that there is a high probability of the human rac…”

“Their version of the SAP (p.21) is essentially the same as Carter’s 1974 version.”

“The shift of the measure (say calibrated for a fixed comoving density of observers making a constant number of observations per time) from being uniform in the time to having the weighting factors of the inverse three-volume (from the spatial density averaging) and of very nearly the inverse square of the time (from t…”

“f the Galactic age (Hart, 1975; Jones, 1976; Tipler, 1980, 1981). In this light, Fermi's legendary question: Where are they? becomes disturbingly pertinent (Brin, 1983; Webb, 2002). In addition, Carter (1983) suggested an independent and powerful anthropic argument for the uniqueness of intelligent life on Earth…”

“Modern-day physics is aware of such anthropocentric biases and – going even further – the more general anthropic principle, also referred to as "observation selection effect" (Bostrom, 2000; 2002; Carter, 1983).”

“If the origination of TI is encapsulated by a Poisson process (e.g., Carter 1983; Spiegel & Turner 2012; Scharf & Cronin 2016), we can introduce a uniform rate parameter λL for the emergence of TI and a “habitability interval” tL, which is the time over which TI could arise; both these parameters…”

“That such a birthrate may be defined with an associated time interval between births has been discussed by Carter (1983) and Gott (1993) in terms of convergent evolution and the coincidence of timescales between the remaining main sequence lifetime of the Sun, the age of the Earth, and the…”

“This is generally agreed upon both by those who attempt to use this fine tuning to support theism, as in the references above, and by many scientists who are usually neutral or opposed to such an attempt [22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35].”

“Carter (1983)). The next question we should ask is : How big does the catastrophe at each point in the history of Earth need to be in order to be consistent with the existence of intelligent observers at t=t0? Notice that the observers we are asking about here need not be us, humans, in either a morphological, phyloge…”

“Improved epistemological and methodological understanding of our properties as intelligent observers, as well as physical, chemical and other pre-conditions necessary for the existence of such observers (Carter, 1983; Livio, 1999).”

“made a distinction between the ‘weak’ and ‘strong’ forms of the AP [4].”

“A suitable Bayesian null model already exists: the ‘critical steps’ model [70,71] predicts there were roughly four innately rare, contingent steps on the path to observers (us) that were roughly evenly spaced , and are argued to have involved reorganizations of the biosphere [12].”

“Consider the simplified Doomsday Argument (Carter and McCrea 1983) for modeling the total number of humans that were ever or will ever be born.”

“Each of the ‘‘major transitions’’ (Maynard Smith and Szathmary, 1997) or ‘‘crit-ical steps’’ (Carter, 1983) in evolution opened up huge new parts of the total morphospace—parts that without the transition in question would have been not only unreachable but perhaps inconceivable as well.”

“In this context, it is relevant to mention a very important issue raised by Carter in his paper on biological evolution (Carter, 1983) that cosmologists would run a risk of error in the”

“Alternatively, they consider that the emergence of complex life should be proportional to some greater powers of each of these quantities, if given by a sequence of hard steps, as in [116].”

“12 the term “cognition principle” (Carter 1983) may have been less problematic than the somewhat inappropriate term AP.”

“In fact, there is reason to believe that life necessarily takes billions of years to develop intelligence: the similarity to stellar lifetimes has been taken as evidence that this may be the minimum possible time required [44] (though see [45] for the alternative interpretation that time spent is the circumstellar hab…”

“…late in Earth’s window of habitability and to estimate the number of critical, highly improbable steps in the evolution of intelligent life on Earth (Carter 1983; Hanson 1998a,b; Flambaum 2003; Watson 2004; Carter 2008; Watson 2008; ´Cirkovi´c et al. 2009; Aldous 2012; Bostrom 2013; Lingam & Loeb…”

“Our Principle of Mediocrity inference based on us being technologically early is not the same logic as the so-called Doomsday Argument (Carter & McCrea 1983; Gott 1993; Leslie 1996; Bostrom 2002), which itself is an unjustified extension of the German Tank Problem.”

“Our results provide a new perspective on the so-called “coincidence problem”, why do we observe Ωm ∼ ΩΛ? [261] The answer comes naturally if we consider the history of Sun-like star formation, as the number of habitable planets peaks around present time for m ∼ 1M .”

“The approximate equality of T i and T for the Solar System, along with the assumption that f (T) and f i T i are independent, led Carter (1983) to conclude that intelligent life is rare in the universe.”

“Lastly, one may regard the origin of life as a ‘hard step’ process, whereby each step in a chain of necessary innovations is proportional to disequilibrium, leading to the concatenation of all processes being proportional to some integer [14].”

“This conclusion would fly in the face of the Principle of Mediocrity (Gott, 1993; Franck et al. , 2007), but that Principle is a purely philosophical argument, not a scientific one, and opposite philosophical positions have been taken based on the Anthropic Principle of post-selection (Carter, 1983).”

“Perhaps the most well-known sources are (Carter 1983), Gott (1993), and Leslie (1989)(3).”

“s is generally agreed upon both by those who attempt to use this fine tuning to support theism, as in the references above, and by many scientists who are usually neutral or opposed to such an attempt [22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35]. Of course no one knows what other forms of life might be poss…”

“One rather arcane challenge that has occurred to me is the application of the Carter-Leslie-Nielsen-Gott doomsday argument [5, 6, 7, 8, 9, 10] to the afterlife.”

“As a prescription for ascribing a priori probability weightings to the eventuality of finding oneself in the position of particular conceivable observers, the anthropic principle was originally developed for application to problems of cosmology [1] and biology [2].”

“We can consider the existence of thalamo-cortical reverberation as an accompanying phenomenon, or even as a key part of the processes of human consciousness (Faber [9, 22, 31]).”

“Such an argument has had its fair share of defenders (e.g. Bostrom, 2013; Leslie, 2002) since its formulation by Carter (1983).”

“The anthropic principle has many variants in two categories: those predicated on the universe being somehow fine-tuned to support life (famously espoused by Barrow and Tipler [1]), and the incorporation of selection bias into reasoning about the universe, described originally by Carter [4].”

“They were here first, they occupy almost every possible niche from over a kilometre deep in the crust [100] to the upper troposphere [101], and, given the likely capacity of archaea and bacteria to survive in suspension in salt crystals for geological times [102,103], they will be here long after we are extinct [104].”

“Estimates of the time scale for life to emerge from non-life range from a few million years (Oberbeck and Fogelman, 1989; Lazcano and Miller, 1994) up to billions of years or even longer (Carter, 1983).”

“Although Carter fi rst presented the argument in a Bayesian framework (Carter 1983), Francis Crick had previously emphasized the same concept (1981), as acknowledged by Carter.”

“However, it is evident that these evolutionary transitions may not necessarily be independent of planetary processes, as originally hypothesized (by Carter [3]).”

“This results from a model—due to Carter and McCrea (1983)—that the probability of observers increases with t n where t is time available and n is around 3; hence a red dwarf with a main sequence lifetime 100 times greater than the Sun is one million times more likelytoproduce observers.”

“There are 188 confirmed impact craters on Earth at the time of this writing (February 2016).15 There is, obviously, a relationship between the size of the impactor and the size of the crater created, although the relationship is non-linear and complicated, needing to account for properties such as chemical composition…”