Science doesn't deal in absolutes, it deals in uncertainty and quality - testing against uncertainty beyond reasonable doubt.

From a standpoint of uncertainty and quality we can observe that the gaps are gone. Thus the theological/religious game against observable knowledge is over.

"You say revision, I say mistake."

Context? I didn't say "revision".

"Science doesn't explain everything. Neither does religion."

Religion explains nothing, now that it can't predict 'gaps'. Science is in the business to make predictions on everything that is (the universe), but obviously it doesn't claim to predict everything. That is not a bug, it is a feature - compare with how religion tried the latter.

"It is not exactly analogous. ... They actually get to see it as it was."

Fair enough, I overstated. We seem to agree on its existence.

On the other hand it means astronomers have a smaller samples of today's galaxies et cetera.

"Furthermore, the second idea is realizable. We already run primitive ancestor simulations ...".

Yes, we can research some questions by simulations. But we can't simulate what happened, know all the missing factors et cetera, up to the point that it equals what astronomer's observations reveal.

To hash this out a bit, entropy is not the sum of physical laws. It isn't even a law. Entropy is a property of macroscale physics (i.e. summed over microscales in statistical physics). But there is a local law of thermodynamics (TD) that states that entropy in closed systems is maximized over time.

In this context physicists are still arguing if entropy is a property of the whole universe, a proposition that is even iffier than attributing an energy to the whole system. It seems that you can, even independently of attributing energy which latter you do from the global geometry or the system behavior. But then you have to use the holographic principle just as for black holes. And you see that it is increasing over cosmological time.

The only thing that law, the 2nd law of TD, says is that there exist irreversible systems. Its microscale statistical physics elaboration is that entropy is a measure of the energy states that are available to the system at its given energy.

Superficially the 2nd law describes disorder. But it is wrong to say that it equals an increase of disorder, since in very constrained systems the most ordered ones have the highest entropy.

Instead its use is in TD. Life is like a refrigerator, in an open system (Earth radiation to space) with an energy source (Sun) it can locally "freeze out" ordered states, as long as the energy differential is there. But the reason it can continue to do so over cosmic time is because the universe is expanding, so the entropy density is never maximized. Incidentally, nothing is "anti-enthropic", since entropy is a statistical property of all large quantum systems.

As for astrobiology here, the universe evolved complex structures early on. The oldest stars and their galaxies are more than 13 billion years old, and the oldest known planet is ~ 12.7 billion years old. Physicist Sean Carroll notes that complexity of the universe, in almost all definitions, has been increasing over cosmological time. But it has also already maximized since we are now in the exponentially expanding dark energy dominated era. Complexity will continue to dilute to zero as massenergy density does. That is apparent in your images by the way.

Earth is but 1/3 of the universe age, but it evolved life right away and complex multicellular life, starting with cyanobacteria differentiation, with the oxygenation event after ~ 2 billion years. Intelligence is, as the elephant trunk, not assured what we know, but happened ~ 2 billion years after that.

I would hence assume that the population of inhabited planets that saw complexity started to become dense ~ 11 billion years ago, and the population of inhabited planets that saw intelligence started to become dense ~ 9 billion years ago. Since we can approximate such stochastic processes with a Poisson process at first blush, its exponential increase can very well be described as a "pulse". (But a non-correlated such mind, excepting transpermia and space faring colonization.)

Given that most habitable planets will be around M stars that can live for ~ 100 billion years and a superEarth can keep its atmosphere for ~ 20 billion years, the pulse has reached roughly maximum density long since but not yet started to die out. (I'm convolving colonization into that, because it is much faster, cheaper, less risky and more rewarding to colonize Oort clouds than planets - the galactic Oort cloud is likely already filled with a stable density of silent, socially and biologically divergent, biospheres. Or it isn't and the result is unlikely to differ.) Earth will die before that.

Um, what? The "time machine" of sediments is exactly analogous to the time machine of redshift. There is even the same fossils, e.g. the uncovered "relic" of the cosmic microwave background as (re)combination happens. There is even a familiar spottiness in the astronomical sediments, due to absorption from molecular clouds et cetera.

Since none of the two suggested ideas are physically realizable I'm not going to bother with them.

But I have one nitpick:

"For example we need to gain a better understanding of the following: ... Effects of the Lake Toba supervolcanic eruptions on human migration and evolution".

Since the null hypothesis is that no effect is observable, and AFAIK no effect is observable, I don't see why this item made the list. We can't add observations (such as the Lake Toba eruption) if there is no known correlation to migration and evolution.

I really dislike this old idea, mainly because it was supported by Hoyle et al during his "steady state universe with transpermia" pseudo-creationist period. (But it can have older roots.)

Besides being a cherry-pick, as you yourself notes at the end "evolution can produce trillions of species without ever selecting for high-intelligence". Confusing growth processes with any of the many ways to measure complexity is the other sleight of hand often used. Parasitic simplification is at least as common (with other half of species parasites), meaning there is no specific trend but a Gouldian diffusion to fill up a niche space. Mass extinctions tests that nicely, with diversity recovering to random levels, it can be a more or less complex system after a ME. [I don't have that ref handy.]

Other minutiae is that biologists haven't checked with planetary scientists. Mojzics et al has shown that any realistic intensity of late bombardment can't sterilize a planet, cells procreate and disperse faster than impactors sterilize crust. (There is even a Goldilocks zone ~ 1 km down where crust busters are survivable somewhere else on a planet.)

The earliest potential trace fossils are now the Isua BIFs @ 3.8 Ga bp, since small scale isotope analysis has shown that the later metamorphosed rocks were originally biologically deposited. So with Mojzics et al in mind, we don't really know when life appeared, because of later plate tectonics - few older rocks. A simple model [of my own] using the latest protein fold phylogenies gives a (linear, btw) extrapolation of the first gene ~ 4.10 Ga bp, which is reasonably after the first oceans appeared ~ 4.25 Ga bp [from the Jack Hill zirconium/diamond evidence.]

Other concerns raised: - Transpermia. Can't compete with local abiogenesis rates with the latest pathways such as Lane & Martin, or Russell et al. Even a martian tramway raining down flash frozen spores has too low transfer rate to make it the likeliest pathway if you take experimentally observed factors of survivability et cetera into account.

- Fermi question. Too unconstrained due to potentially unobservable pathways (silent civilizations), making for false negatives. Need observed positives for making the full Drake equation a useful estimate. (The short DE for life at large works well for potentially observable inhabited, oxygenated worlds on the other hand, as we will only look for positives.)

Not likely, since deterministic chaos prevents "programming". As for the process that results in universes, it is quantum mechanics on the quantum void. I.e. no one can "create" a universe, since such a system would have excess energy which a universe can't have.

Religion has always been its own worst enemy. When did "moderates" stand up and condemn what their extremists are capable of under their religious myths?

"Science is AWESOME - but it is also flawed. Not necessarily the process, but we make mistakes in our assumptions all the time. The prevailing winds of science change constantly."

Your hypothesis on science is flawed, and rejected by observation. As Sean Carroll notes, "The Laws Underlying The Physics of Everyday Life Are Completely Understood". [ http://www.preposterousuniverse.com/blog/2010/09/23/the-laws.../ ] Science, while revisable, converges on robust facts and theories.

It is too late to imagine "mistakes", and the gaps are gone too. We now know that the universe _must_ be a result of a spontaneous process, that independent of that there _can't_ be any soul et cetera. And as for the deist cop out, the cosmology analysis now stands between multiverses, so physics is local, or naturalness, so physics is forced. Eg magic can't slip in there either.

Game over!

Of course, it will take magic believers decades to get to grips with the facts. For example, officially the catholic church has no magic agency at the moment, because their latest bid was that it wouldn't have to create a universe but it absolutely had to create a unique human breeder pair. So that agency was found false 2011 from sequencing the neanderthal nuclear genome. And "remarkably", that church hasn't acknowledged their problem with truth yet. As per the usual scam practice.

"Regardless of culture people attribute agency to the supernatural. This is despite the fact that nothing supernatural (perhaps by definition) can be empirically observed,".

I don't think science should make theological claims. People attribute agency, period. What happens after is that we observe that much of that is amenable to observation.

For example the non-existence of global floods (19th century). The inefficacy of intercessory prayer (2006). The non-existence of a single human breeder pair (2011). That the universe to 10^22:1 or in other words 100 % must be a result of a spontaneous process (as per curvature measure of initial energy; 2012). That the LHC completion of the Standard Model means any ideas of souls/afterlife/rebirth would need 10^3 times the energy they are allowed from QED precision measurements (2013).

The same goes for the description of abrahamistic religions in point 1-3, I don't think science should be limited to the observation of those. Religions started AFAIK out as attributing agency spurred by our ability to see patterns and imagine agency. Often looking for human analogs.

Granted, some religions grappled with explanation, some with death, some with destiny. But I don't think we can model religion on those specifically.

As for eternity, I think Sean Carroll's latest summer school in cosmology was enlightening. The absence of eternity, which LHC may imply (not quite 3 sigma for a quasi-stable vacuum), may be necessary to get rid of Boltzmann Brains. Eg the problem isn't that quantum mechanics isn't spontaneously spawning things, like universes from the quantum void, the problem is that it does so too eagerly, like BB fluctuations out of a thermal vacuum. Meaning, magic is not even on the horizon today, the real problem is that nature is too "creative".

"Since the first members of Homo lived 2.3 million years ago (Aiello and Wells, 2002), Au. sediba obviously couldn't have been their ancestor ... This is the final nail in the coffin of the idea that Au. sediba was the ancestor of modern humans".

Quite the opposite, in fact. The mosaic with human traits shows conclusively that no single trait is enough to proclaim whether a fossil is human or not. (And I've seen anthropologists note this. Me, I'm interested in astrobiology.) And that is precisely the case with the single Homo-like maxilla from, arguably as well as far as I know, 2.3 Ma bp, which only Homo-like trait is its parabolic curvature.

So what has happened, everything else alike, is that these new finds have opened up the case for Au. sediba as an ancestor of modern humans. And this is what seems to be the reception among anthropologists, nothing conclusive either way but a more open field.

"a study by chemists Addy Pross and Robert Pascal"

I thought for a moment I had missed something. But no, it is the same sweeping ideas that are so often promoted in this area.

I can understand that they are alluring. But they are based on some fundamental misunderstandings of biology. From my viewpoint of studying astrobiology, here they are:

- The idea that we need new mechanisms for chemical evolution.

First, we observe that chemical evolution works throughout time and space in the universe.

Second, the speed with which life was established on Earth speaks for an easy and/or often enough attempted process transitioning to biological evolution.

- The idea that evolution isn't falsifiable.

Evolution gives phylogenies, which by construction are enormously constrained combinatorial networks, a handful of potential pathways (species lineages) in a truly vast space of networks. We don't need,nor ask for, the exact pathways as local resolution can be too low, yet the precision of the entire network staggering. (Many orders of magnitude certainty.)

They are tested by adding species. Famously "a precambrian rabbit" falsifies the standard phylogeny. Here it would be "pre-Earth genes", say. Eminently testable, all gene or protein fold phylogenies converge on ~ 4 billion years as the earliest "rabbit".

- The idea that biology is an equilibrium and/or stability regime.

The thermodynamics of the planet (biosphere driven by the Sun, radiating to space) rejects that. The evolutionary biological process is as such very little coupled to thermodynamics and there is no inherent ecological (population) stability.

Instead, where is astrobiology today?

- Lane & Martin has shown that classical bottleneck constraints (chicken-or-egg problems) makes alkaline hydrothermal vent chemistry preceding earliest autotroph metabolism. As expected, these mechanisms were as they note in the paper homologous chemical networks.

- Thermodynamics shows that a) RNA is the only pre-protein nucleotide that fulfill the thermodynamic bound for replicators, b) a random strand 'gas' population of RNA _will_ crystallize to a replicator within ~ 30 000 years in the phosphate activating environment of alkaline hydrothermal vents.

The pathways from replicator strands to genomes are legion, but the simplest goes through a simplest possible brwonian ratchet making RNA strand replication one way and unchained from vent thermal environment. Coincidentally, the minimum ratchet is a 3 basepair codon polypeptide, the initially random sequencing (no function except ratcheting) consistent with early fold properties (random peptides outside of fold function).

These two bottleneck systems marry well, the first genomes would support local organics producing metabolic cellular compartments and vice versa.

To clarify, the oxygen of gas giants comes from their radiation belts affecting the surface ice. Jupiter is extremely large, and it may be that more typical giants supplies less.

Also, there are at least 2 hominids that have become ~ 2 million years old, A. afarensis and H. erectus.

What do I think? As interested in astrobiology I think the obvious existence of silent pathways makes the Fermi question "where are they" too unconstrained by false negatives to be "a big question". The "big question" here then remains the age old "are we alone".

A silent pathway would be the natural expansion out of a planetary system to the Oort cloud. It is the largest step on the exponential scale of technological and material resources. But it has also the needed material for transportable biospheres without the associated cost and risk of descending deep gravitational wells.

As for the astrobiology here:

1. Selection bias.

That is asked from a position of selection bias, we _are_ the first if we want to outdefine other intelligences we have observed.

More pertinent, biologists use to estimate that language capable intelligence may be as rare a trait as the elephant's trunk. On the other hand they have also come up with estimates based on diversity, which is more or less recovered after mass extinctions. Hence we have independent observable "worlds", and 1 out of 4 (3 large extinctions with land animals) made us.

All galaxies got started after reionization, so the parts of MW is about 13.5 billion years old. The first habitable planets aggregated shortly after the first star generation, the oldest known exoplanet is ~ 13 billion years old. We can expect the first life is about as old.

Then it takes billions of years to oxygenate a biosphere, which is a prerequisite for complex multicellular life. In our case ~ 2 billion years, but we can see that the oceans were still largely uninhabitable until cyanobacteria also regulated a nitrogen cycle. (Which put a stop to anoxic sulfur conditions.)

However, it is believed that the ocean of Europa has been supplied with large amounts of oxygen some hundred of million years after the ice cover formed. This seems to be a generic mechanism for the tidal habitable zone of gas giants. And the biospheres of ice moons are easily 10s of times larger than terrestrial oceans. So early intelligent life is most likely found there.

2. Life span of species.

Typical lifetime of mammal species is ~ 1 million years, and Homo seems to lie there.

5. Biospheres.

There are two viable cosmological economies, given the distances and the universal speed limit:

Information barter and colonization. As I showed above, Oort cloud colonization is likely and means silent dispersal. In any case, colonization means dispersal: population genetics shows that you need one crossbreeding/generation to keep a population from speciation. (Regardless of the size of the population, funnily enough.)

[Wormholes break general relativity with their closed timelike curves, so they can't exist - or the universe would have exploded.

Alcubierre is a viable GR solution but can't be used. If such a solution is created going FTL there is no way to put mass there to go FTL, since we can't break the universal speed limit for massive particles in the first place.]