Climate refugia and migration requirements in complex landscapes

All of today's species have proven their ability to cope with climate change during the glacial‐interglacial cycles of the Quaternary, but future migration requirements may be different regarding speed, direction, geographic barriers, and availability of nearby climate refugia. Here, we contribute a landscape‐level climatic analysis of postglacial vs. projected future migration requirements for 24 common western North American tree species. Using a recently developed velocity of climate change algorithm, we quantify required migration velocities for all populations of species to track climate habitat, based on projections from general circulation models for the 2080s and the last glacial maximum, 21 000 yr ago. Specifically, we ask if nearby climate refugia exist for at least some populations within species ranges and whether the current landscape position of species imply qualitatively different migration requirements in the future compared to those during glacial‐interglacial cycles. Results showed that velocities to reach the nearest climate refugia in the future still exceed the fastest reconstructed post‐glacial migration requirements, but not by orders of magnitude. Regarding landscape positions, we find a low correlation among past and future migration requirements (r = 0.38), suggesting that qualitatively different migration patterns may emerge in the future for some species. Species identified as occupying landscape positions requiring disproportionally faster migration requirements in the future include whitebark pine, pinyon pine, and coast redwood. We discuss uncertainties of our analytical approach as well as implications for human‐assisted migration and conservation action to address climate change.     

Functional properties of the isomorphic biphasic algal life cycle

Many species of marine algae have life cycles that involve multipleseparate, free-living phases that frequently differ in ploidylevels. These complex life cycles have received increasing scientificattention over the past few decades, due to their usefulnessfor both ecological and evolutionary studies. I present a synthesisof our current knowledge of the ecological functioning and evolutionaryimplications of the isomorphic, biphasic life cycles commonlyfound in many species of marine algae. There are both costsand benefits to life cycles with 2 morphologically similar butseparate, free-living phases that differ in ploidy levels (haploidsand diploids). Evolutionary theory predicts that the existenceof subtle yet important differences between the phases may bewhat allows these life cycles to be maintained. Different phasesof the same species can vary in abundance, in demographic parameterssuch as mortality and fecundity, in their physiology, and intheir resistance to herbivory. Some taxonomic groups withinthe red algae have received significant attention toward theseissues, while our knowledge of these properties for brown andgreen algae remains limited.     

Identity,prudential concern,and extended lives

Recent advances in human genetics suggest that it may become possible to genetically manipulate telomerase and embryonic stem cells to alter the mechanisms of aging and extend the human life span. But a life span significantly longer than the present norm would be undesirable because it would severely weaken the connections between past- and future-oriented mental states and in turn the psychological grounds for personal identity and prudential concern for our future selves. In addition, the collective effects of longer lives might lower the quality of life for all people. These two problems provide reasons against genetic manipulation of cells to alter the length of the human life span.     

Genomics and the Ark: an ecocentric perspective on human history

Views of ourselves in relationship to the rest of the biosphere are changing. Theocentric and anthropocentric perspectives are giving way to more ecocentric views on the history, present, and future of humankind. Novel sciences, such as genomics, have deepened and broadened our understanding of the process of anthropogenesis, the coming into being of humans. Genomics suggests that early human history must be regarded as a complex narrative of evolving ecosystems, in which human evolution both influenced and was influenced by the evolution of companion species. During the agricultural revolution, human beings designed small-scale artificial ecosystems or evolutionary "Arks," in which networks of plants, animals, and microorganisms coevolved. Currently, our attitude towards this process seems subject to a paradoxical reversal. The boundaries of the Ark have dramatically broadened, and genomics is not only being used to increase our understanding of our ecological past, but may also help us to conserve, reconstruct, or even revivify species and ecosystems to whose degradation or (near) extinction we have contributed. This article explores the role of genomics in the elaboration of a more ecocentric view of ourselves with the help of two examples, namely the renaissance of Paleolithic diets and of Pleistocene parks. It argues that an understanding of the world in ecocentric terms requires new partnerships and mutually beneficial forms of collaboration and convergence between life sciences, social sciences, and the humanities.     

The Biology of Time and Death

The steady flow of solar energy through prebiotic chemical systems forced them to undergo material cycles, and this cycling was inherited by living organisms. Organisms whose cycling synchronized with periodic phenomena, such as day/night and seasonal variations were favored. At a later stage, evolution also favored organisms that, besides of a synchronized cycling, developed a ‘sense of time’ to cope with non-cyclic and unique events in the environment. In the case of human beings, this ‘sense of time’ was used to detect causal chains (cause → effect), combine them to produce dynamic models of reality, and transform real time scales into mental time scales (it takes a moment to remember a year-long phenomenon). The ‘sense of time’ constituted a decisive evolutive advantage, because it enables humans to analyze a multitude of future possibilities, and choose the most promising one. Yet ‘sense of time’ is just an empty metaphore, because it is not a true ‘sense’, and we ignore what ‘time’ really is. Most scientific disciplines simply take for granted that there is a ‘time flowing from future to past’. Biologists instead, cannot adopt this attitude because ‘time’ may very well be an intrinsic property of our mind, i.e., a peculiar aspect of brain physiology.     

Experimental evolution of multicellularity using microbial pseudo-organisms

In a major evolutionary transition to a new level of organization, internal conflicts must be controlled before the transition can truly be successful. One such transition is that from single cells to multicellularity. Conflicts among cells in multicellular organisms can be greatly reduced if they consist of genetically identical clones. However, mutations to cheaters that experience one round of within-individual selection could still be a problem, particularly for certain life cycles. We propose an experimental evolution method to investigate this issue, using micro-organisms to construct multicellular pseudo-organisms, which can be evolved under different artificial life cycles. These experiments can be used to test the importance of various life cycle features in maintaining cooperation. They include structured reproduction, in which small propagule size reduces within-individual genetic variation. They also include structured growth, which increases local relatedness within individual bodies. Our method provides a novel way to test how different life cycles favour cooperation, even for life cycles that do not exist.     

Bioenergetics of early life: Coupling of reaction networks and compartments may have sparked the first life forms

Living cells are powered by intricate networks of chemical reactions of thousands of molecules. Understanding how living systems emerged through the assembly of chemical processes is one of the biggest challenges in science. Subject Categories: Biotechnology & Synthetic Biology, Evolution & Ecology, Metabolism

How can chemistry turn into biology? How can living cells be built from molecules? These are fundamental questions in biology and, despite much research efforts, remain unanswered. Yet, the past two decades have seen considerable advances in our knowledge of how and which (bio)physical and (bio)chemical processes could have driven the emergence of the first living cells. These achievements have led not only to a better understanding of the molecular origins of life, but also spurred significant developments in synthetic biology, biophysics and supramolecular chemistry. Although the exact events that sparked life on Earth will quite likely remain a mystery, at least partially, exploring the chemical origins of life offers clues about our primordial past and could contribute to shaping our future.

Although the exact events that sparked life on Earth will quite likely remain a mystery […] exploring the chemical origins of life offers clues about our primordial past and could contribute to shaping our future.

     

Human responses to the geophysical daily, annual and lunar cycles

Collectively the daily, seasonal, lunar and tidal geophysical cycles regulate much of the temporal biology of life on Earth. The increasing isolation of human societies from these geophysical cycles, as a result of improved living conditions, high-quality nutrition and 24/7 working practices, have led many to believe that human biology functions independently of them. Yet recent studies have highlighted the dominant role that our circadian clock plays in the organisation of 24 hour patterns of behaviour and physiology. Preferred wake and sleep times are to a large extent driven by an endogenous temporal program that uses sunlight as an entraining cue. The alarm clock can drive human activity rhythms but has little direct effect on our endogenous 24 hour physiology. In many situations, our biology and our society appear to be in serious opposition, and the damaging consequences to our health under these circumstances are increasingly recognised. The seasons dominate the lives of non-equatorial species, and until recently, they also had a marked influence on much of human biology. Despite human isolation from seasonal changes in temperature, food and photoperiod in the industrialised nations, the seasons still appear to have a small, but significant, impact upon when individuals are born and many aspects of health. The seasonal changes that modulate our biology, and how these factors might interact with the social and metabolic status of the individual to drive seasonal effects, are still poorly understood. Lunar cycles had, and continue to have, an influence upon human culture, though despite a persistent belief that our mental health and other behaviours are modulated by the phase of the moon, there is no solid evidence that human biology is in any way regulated by the lunar cycle.     

Origins of signalling and memory: matters of life versus death

This review focuses on the principles in cell-cell communication and cellular ability to respond to external chemical changes which have been so crucial for the development of life on planet Earth. We now know that the capacity of free-living organisms which evolved more than a billion years ago to respond to intercellular signal molecules, originating either from themselves or from other sources in their vicinity, is so similar possibly even more sophisticated - to that of the cells in our own body, and these findings have had a major impact on our struggle to understand how life has evolved and how it can be maintained. Attention is drawn to the very important topic of mechanisms in cell death, being seen as an aggressive and very powerful instrument in the continuance of life and ability of life to proliferate into a plethora of new species, and use insulin-related material as our paradigm. Such signal molecules (hormones) may have played a major role in cellular maintenance throughout evolution.     

LIFE-CENTERED ETHICS, AND THE HUMAN FUTURE IN SPACE

In the future, human destiny may depend on our ethics. In particular, biotechnology and expansion in space can transform life, raising profound questions. Guidance may be found in Life‐centered ethics, as biotic ethics that value the basic patterns of organic gene/protein life, and as panbiotic ethics that always seek to expand life. These life‐centered principles can be based on scientific insights into the unique place of life in nature, and the biological unity of all life. Belonging to life then implies a human purpose: to safeguard and propagate life. Expansion in space will advance this purpose but will also raise basic questions. Should we expand all life or only intelligent life? Should we aim to create populations of trillions? Should we seed other solar systems? How far can we change but still preserve the human species, and life itself? The future of all life may be in our hands, and it can depend on our guiding ethics whether life will fulfil its full potentials. Given such profound powers, life‐centered ethics can best secure future generations. Our descendants may then understand nature more deeply, and seek to extend life indefinitely. In that future, our human existence can find a cosmic purpose.     

From Eden to a hell of uniformity? directed evolution in humans

For the first time during evolution of life on this planet, a species has acquired the ability to direct its own genetic destiny. Following 200,000 years of evolution, modern man now has the technologies not only to eradicate genetic disease but also to prolong life and enhance desired physical and mental traits. These technologies include preimplantation diagnosis, cloning, and gene therapy in the germline on native chromosomes or by adding artificial ones. At first glance, we should all be in favor of eliminating genetic diseases and enhancing genetic traits. Evolutionary considerations, however, uncover hidden dangers and suggest caution against the total embracement of such actions. The first major concern is that the genome will never be a completely reliable crystal ball for predicting human phenotypes. This is especially true for predictions concerning the performance of alleles in future generations whose populations might be subjected to different environmental and social challenges. The second, and perhaps more important, concern is that the end result of germline intervention and genetic enhancement will likely lead to the impoverishment of gene variants in the human population and deprive us of one of our most valued assets for survival in the future, our genetic diversity.     

The present, past and future of human-caused extinctions

This paper re-evaluates whether we are really at the start of a mass extinction caused by humans. I consider the present, past and future of human-caused extinctions. As regards the present, estimates of extinction rates based on Red Data Books underestimate real values by a large factor, because the books evaluate only those species that have attracted specific attention and searches. Especially in tropical areas with few resident biologists, many poorly known species go extinct without having been the object of specific attention, and others disappear even before being described. A 'green list' of species known to be secure is needed to complement 'red books' of species known to be extinct. As regards the past, it is now clear that the first arrival of humans at any oceanic island with no previous human inhabitants has always precipitated a mass extinction in the island biota. Well-known victims include New Zealand's moas, Madagascar's giant lemurs, and scores of bird species on Hawaii and other tropical Pacific islands. Late-Pleistocene or Holocene extinctions of large mammals after the first arrival of humans in North America, South America and Australia may also have been caused by humans. Hence human-caused mass extinction is not a hypothesis for the future but an event that has been underway for thousands of years. As regards the future, consideration of the main mechanisms of human-caused extinctions (overhunting, effects of introduced species, habitat destruction, and secondary ripple effects) indicates that the rate of extinction is accelerating.(ABSTRACT TRUNCATED AT 250 WORDS)     

Human immunodeficiency virus type 2 envelope glycoprotein binds to CD8 as well as to CD4 molecules on human T cells.

We report here that human immunodeficiency virus type 2 (HIV-2) envelope glycoprotein (gp105), but not HIV-1 gp120, can bind to CD8 molecules as well as to CD4 molecules on human T cells. This phenomenon may lead to differences in the life cycles of HIV-1 and HIV-2, and it may be related to the differences in disease manifestations of HIV-1 and HIV-2 infection, including longer survival of HIV-2-infected patients.     

Genetic approaches to memory storage.

The ability to remember is perhaps the most significant and distinctive feature of our mental life. We are who we are largely because of what we have learned and what we remember. In turn, impairments in learning and memory can lead to disorders that range from the moderately inconvenient benign senescent forgetfulness associated with normal aging to the devastating memory losses associated with Alzheimer disease. Of the various, higher-cognitive abilities that human beings possess, such as reasoning and language, memory is the only one that can be studied effectively in simple experimental organisms that are accessible to genetic manipulation, such as snails, flies and mice. In these organisms, the effectiveness of genetic approaches in the study of memory has improved significantly in the past five years. Below we review these advances.     

Why the world needs protists!

In this brief review, literature references are given to researches--involving diverse species of protists--that support the author's firm conviction that the biological world of today absolutely requires the presence of numerous of these generally small and unicelled organisms if it is to survive. Examples supplied come from areas within the field of protistology sensu lato as widely separated as basic phycological research on photosynthesis and protozoological/medical/biomedical investigations on malaria and other pathogens of human beings. Emphasis is primarily on the most relevant works of the past 10-15 years, although historically highly significant papers of older vintage require at least indirect--and occasionally direct--citation.     

Conserved and divergent paths that regulate self-renewal in mouse and human embryonic stem cells

The past few years have seen remarkable progress in our understanding of embryonic stem cell (ES cell) biology. The necessity of examining human ES cells in culture, coupled with the wealth of genomic data and the multiplicity of cell lines available, has enabled researchers to identify critical conserved pathways regulating self-renewal and identify markers that tightly correlate with the ES cell state. Comparison across species has suggested additional pathways likely to be important in long-term self-renewal of ES cells including heterochronic genes, microRNAs, genes involved in telomeric regulation, and polycomb repressors. In this review, we have discussed information on molecules known to be important in ES cell self-renewal or blastocyst development and highlighted known differences between mouse and human ES cells. We suggest that several additional pathways required for self-renewal remain to be discovered and these likely include genes involved in antisense regulation, microRNAs, as well as additional global repressive pathways and novel genes. We suggest that cross species comparisons using large-scale genomic analysis tools are likely to reveal conserved and divergent paths required for ES cell self-renewal and will allow us to derive ES lines from species and strains where this has been difficult.     

Archaeology,demography and life history theory together can help us explain past and present population patterns

Population matters. Demographic patterns are both a cause and a consequence of human behaviour in other important domains, such as subsistence, cooperation, politics and culture. Demographers interested in contemporary and recent historical populations have rich data at their fingertips; the importance of demography means many interested parties have gathered demographic data, much of which is now readily available for all to explore. Those interested in the demography of the distant past are not so fortunate, given the lack of written records. Nevertheless, the emergence in recent years of a new interest in the demography of ancient populations has seen the development of a range of new methods for piecing together archaeological, skeletal and DNA evidence to reconstruct past population patterns. These efforts have found evidence in support of the view that the relatively low long-term population growth rates of prehistoric human populations, albeit ultimately conditioned by carrying capacities, may have been owing to ‘boom–bust’ cycles at the regional level; rapid population growth, followed by population decline. In fact, this archaeological research may have come to the same conclusion as some contemporary demographers: that demography can be remarkably hard to predict, at least in the short term. It also fits with evidence from biology that primates, and particularly humans, may be adapted to environmental variability, leading to associated demographic stochasticity. This evidence of the fluctuating nature of human demographic patterns may be of considerable significance in understanding our species'' evolution, and of understanding what our species future demographic trajectories might be.This article is part of the theme issue ‘Cross-disciplinary approaches to prehistoric demography’.     

What Justifies a Future with Humans in It?

Antinatalist commentators recommend that humanity bring itself to a close, on the theory that pain and suffering override the value of any possible life. Other commentators do not require the voluntary extinction of human beings, but they defend that outcome if people were to choose against having children. Against such views, Richard Kraut has defended a general moral obligation to people the future with human beings until the workings of the universe render such efforts impossible. Kraut advances this view on the grounds that we are obliged to exercise beneficence toward others and on the grounds that the goods available in human lives are morally compelling. This account ultimately succeeds in making no more than a prima facie defense of human perpetuation because considerations of beneficence could override – in some cases probably should – override any duty to perpetuate human beings. While the goods of human life may be distinctive, they cannot serve as reason‐giving in regard to their own perpetuation. Ironically, the exercise of beneficence may authorize the extinction of human beings, if it becomes possible to enhance the goods available to human descendants in a way that moves them away from human nature as now given. The defense of a morally obligatory and strictly human future remains elusive, even as it becomes morally desirable to work against Fateful Catastrophes, those human‐caused events that threaten to extinguish existing lives already good and enriching for their bearers.