But runaway positive feedback loops, either greenhouse heating or glaciation-albedo freezing, soon render most planets uninhabitable. "...If life emerges on a planet, it only rarely evolves quickly enough to regulate greenhouse gases and albedo...."

Venus is a likely example of the greenhouse catastrophe, finally losing its water to dissociation by UV radiation in the upper atmosphere. And Mars may exemplify the freezing scenario, eventually losing most of its water, too.

They call lethal outcomes like these, collectively, the "Gaian bottleneck." It is a new way to explain why "the Universe does not seem to be teeming with life." (Actually, we think the universe may be teeming with microbial life, but SETI, at least, has not found any advanced life.)

The two scientists never mention panspermia, but it would make the emergence of life elsewhere even more likely than they suppose. And we think that the genetic programming for life with Gaian stabilizing feedback loops is readily available and need not wait until strictly darwinian evolution may compose it. So, logically, Fermi's paradox is an even bigger puzzle for cosmic ancestry. The barriers to long-lasting, highly evolved life must be formidable.

We think the two Australians deserve an audience. We like their firm predictions, unfettered speculations, and noteworthy observations, like, "The existence of liquid water on the surface of a planet may be a better biosignature than oxygen...." Their article is thought-provoking, well-referenced and currently available on the Internet.

04 Jan 2016

What'sNEW about HGT |

"...We identified 2,714 genes which were specific of human, chimpanzee, or their hominoid ancestor. ...These genes lacked homologues in other species after exhaustive searches...."

The researchers observe that silent DNA is unconstrained and therefore free to explore the entire available sequence space. But these de novo genes "had a median size of 595 nucleotides." That length of DNA has c. 10^358 possible sequences. Not one quintillionth, 10^340, of that sequence space could have been explored within the consensus big-bang universe. Darwinism cannot account for these genes.

Cosmic ancestry, however, expects genetic programming to precede its own expression, as de novo genes demonstrate. These programs may be delivered by various means of horizontal gene transfer (HGT), switched on with new regulatory sequences also coming from HGT, tested, and eventually retained-or-not by natural selection. From the report:

      "...In every genome there are sets of genes which are unique to that particular species i.e. lacking homologues in any other species. How have these genes originated?"
      "...We have found thousands of transcripts that are human and/or chimpanzee-specific and which are likely to have originated de novo from previously non-transcribed regions of the genome. We have observed an enrichment in transcription factor binding sites in the promoter regions of these genes when compared to other species; this is consistent with the idea that the gain of new regulatory motifs results in de novo gene expression. We also show that some of the genes encode new functional proteins expressed in brain or testis, which may have contributed to phenotypic novelties in human evolution."
      "Our analysis was based on multiexonic genes but we have to consider that many recently evolved genes may not have yet acquired the capacity to be spliced.... Therefore, there are probably many more de novo genes than those studied here. The de novo genes constituted about 4% of all expressed multiexonic genes in human and chimpanzee."
      "Several studies have found an excess of genes of very recent origin when compared to older gene classes. This suggests that many young genes are subsequently lost, which is consistent with the relatively constant number of genes observed in a taxon. Our finding that signatures of purifying selection are generally very weak for de novo genes is indeed consistent with a scenario in which many of these genes are dispensable. However, a subset of genes with evidence of translation do display significant signatures of purifying selection, indicating that they correspond to functional genes."