Early Biological Evolution Research Articles

Paleosalinity of the Nanhua Basin (South China) during the Cambrian Explosion

Similar to marine oxygen level and nutrient supply, seawater salinity has also been suggested as an important control on marine biological evolution. However, the potential links between the seawater salinity and Cambrian Explosion remain unclear. Here, we conducted high-resolution analyses of B/Ga and B/K ratios on four typical sections from different water-depth environments to constrain the paleosalinity in the Nanhua Basin (South China) from late Age 2 to Age 3 (~526–515 Ma). Our new data revealed common hypersaline conditions at shallow-water Meishucun (B/Ga = 13.8 ± 2.3 and B/K = 73.5 ± 15.7) and Wangjiaping (B/Ga = 20.6 ± 2.7 and B/K = 101.1 ± 17.1) locales during most of the period from late Age 2 to Age 3. In contrast, combined with the deep-water data in a recent study, middle- to deep-water environments were dominated by brackish to normal seawater salinity, as documented at Zhijin (B/Ga = 8.0 ± 1.1 and B/K = 48.2 ± 4.5), Daotuo (B/Ga = 6.4 ± 1.6 and B/K = 57.6 ± 12.3), Yuanjia (B/Ga = 4.3 ± 2.7), and Zhalagou (B/Ga = 6.1 ± 1.2) locales. Notably, two transient low-salinity intervals (LS1 and LS2) developed in shallow-water regions at ~526 Ma and ~ 518 Ma, respectively, because of increased freshwater inputs, during which the watermass salinity may be inhabitable for early faunas. Combined with previous redox studies, however, transient shallow-water anoxia at ~525 Ma allowed only the development of hypoxia-tolerant sponge faunas during LS1, indicating redox constrains on the early biological evolution. Additionally, although studies indicated rapid oceanic oxygenation within the hypersaline interval between LS1 and LS2, no important biotas occurred at this hypersaline interval, indicating hypersalinity restriction on metazoan diversification. Instead, when normal seawater salinity and oxic watermass were jointly formed during LS2 (~518 Ma), the Chengjiang and Qingjiang biotas experienced notable explosion. Therefore, the influences of the seawater salinity on early life evolution should be given more attention in the future.

Nitrogen geochemistry and abnormal mercury enrichment of shales from the lowermost Cambrian Niutitang Formation in South China: Implications for the marine redox conditions and hydrothermal activity

The Cambrian is an important period for life evolution during the geological history, and the basal Cambrian black shales with widespread occurrence worldwide record important paleoceanographic information during this critical period. The set of shales with stable distribution and thickness of about 200 m is also extensively developed in South China, which provides an important material for studying the marine redox environment, major geological events and biotic evolution. Here we conduct studies on the nitrogen cycle and mercury's abnormal enrichment based on mercury (Hg) concentrations and nitrogen (N) isotope compositions of the shales from the lower Cambrian Niutitang Formation in Tongren area of Guizhou Province, South China. The results show that both Hg and TOC exhibited abnormal enrichments at the bottom of the Niutitang Formation. Mo and U enrichment factors indicated a gradually oxidized redox evolution during the deposition of the Niutitang Formation, with two fluctuated redox cycles from reducing to oxic, and then from dysoxic to oxic conditions in the water column. And the abnormal enrichment of Hg during the early Cambrian may be related to the volcanic and hydrothermal activities. Nitrogen isotope (δ15N) has obvious negative shift at the bottom of the Niutitang Formation, which indicated that nitrogen fixation was enhanced under the anoxic condition in the water column, the organic carbon pool gradually reduced, and phosphorus (P) and other nutrient elements were available, leading to the enhancement of nitrogen fixation and an increase of bioavailable nitrogen in the water column. Nitrogen isotopes recorded the effects of early Cambrian biological evolution and marine redox environment on nutrient element circulation, with contemporaneous volcanic or hydrothermal fluid activities during this period.

The expansion of the Acheulian to the Southeastern Ethiopian Highlands: Insights from the new early Pleistocene site-complex of Melka Wakena

Current models of early hominin biological and cultural evolution are shaped almost entirely by the data accumulated from the East African Rift System (EARS) over the last decades. In contrast, little is known about the archaeological record from the high-elevation regions on either side of the Rift. Melka Wakena is a newly discovered site-complex on the Southeastern Ethiopian Highlands (SEH) (>2300 m above mean sea level) just east of the central sector of the Main Ethiopian Rift (MER), where eight archaeological and two paleontological localities were discovered to date. Nine archaeological horizons from three localities were tested so far, all dated to the second half of the early Pleistocene (∼1.6 to >0.7 Ma). All the lithic assemblages belong to the Acheulian technocomplex. Here we report on geochronological, stratigraphic, paleontological and lithic technological aspects of the tested localities and contextualize them in the broader framework of hominin cultural evolution in eastern Africa. Findings from Melka Wakena, assessed against the backdrop of the few other highland sites (Melka Kunture and Gadeb), support a scenario of expansion rather than dispersal from the Rift to the highlands. When considered in the context of the Rift-highlands interface, results of the first-phase research at Melka Wakena help to parse existing general models into archaeologically testable hypotheses and demonstrate the site’s potential to contribute to research of early prehistory and to understanding the dynamics of early Pleistocene hominin populations in eastern Africa.

Research of Precambrian silicified spheroidal fossils’ preservation mechanism: Fish egg silicified simulation experimental taphonomy

Silicified spheroidal fossils have been found in the Ediacaran Doushantuo Formation in South China. Their organic material was exceptionally well-preserved, thus important to understanding early biological evolution. But the preservation mechanism of the silicified spheroidal fossils was unclear. As a result, research on the preservation mechanism at primal mineralization process was necessary. For this paper, Megalobrama amlycephala eggs were inserted into jars with different silicified concentration solutions. The eggs were immersed in the concentrated solutions for a period of two weeks and were removed afterwards for observation. Once extracted, the fish eggs were found to be separated into various shapes and sizes and rapidly preserved. The experiment showed that the metasomatism and coating were two different kinds of preservation. Upon closer examination of the fish eggs, not all the nuclei were silicified. Additionally, the surface of these eggs was covered by specks of tiny mineral crystals, particularly a tiny mineral that grew vertically in a special form of special biological texture. These tiny minerals helped protect the egg framework and preserved the delicate surface ornamentation. The taphonomy experiment had an important impact and was beneficial to learn more about silicified spheroidal fossils.

The Moon as a recorder of organic evolution in the early solar system: a lunar regolith analog study.

The organic record of Earth older than ∼3.8 Ga has been effectively erased. Some insight is provided to us by meteorites as well as remote and direct observations of asteroids and comets left over from the formation of the Solar System. These primitive objects provide a record of early chemical evolution and a sample of material that has been delivered to Earth's surface throughout the past 4.5 billion years. Yet an effective chronicle of organic evolution on all Solar System objects, including that on planetary surfaces, is more difficult to find. Fortunately, early Earth would not have been the only recipient of organic matter-containing objects in the early Solar System. For example, a recently proposed model suggests the possibility that volatiles, including organic material, remain archived in buried paleoregolith deposits intercalated with lava flows on the Moon. Where asteroids and comets allow the study of processes before planet formation, the lunar record could extend that chronicle to early biological evolution on the planets. In this study, we use selected free and polymeric organic materials to assess the hypothesis that organic matter can survive the effects of heating in the lunar regolith by overlying lava flows. Results indicate that the presence of lunar regolith simulant appears to promote polymerization and, therefore, preservation of organic matter. Once polymerized, the mineral-hosted newly formed organic network is relatively protected from further thermal degradation. Our findings reveal the thermal conditions under which preservation of organic matter on the Moon is viable.

On the Origin of the Canonical Nucleobases: An Assessment of Selection Pressures across Chemical and Early Biological Evolution.

The native bases of RNA and DNA are prominent examples of the narrow selection of organic molecules upon which life is based. How did nature "decide" upon these specific heterocycles? Evidence suggests that many types of heterocycles could have been present on the early Earth. It is therefore likely that the contemporary composition of nucleobases is a result of multiple selection pressures that operated during early chemical and biological evolution. The persistence of the fittest heterocycles in the prebiotic environment towards, for example, hydrolytic and photochemical assaults, may have given some nucleobases a selective advantage for incorporation into the first informational polymers. The prebiotic formation of polymeric nucleic acids employing the native bases remains, however, a challenging problem to reconcile. Hypotheses have proposed that the emerging RNA world may have included many types of nucleobases. This is supported by the extensive utilization of non-canonical nucleobases in extant RNA and the resemblance of many of the modified bases to heterocycles generated in simulated prebiotic chemistry experiments. Selection pressures in the RNA world could have therefore narrowed the composition of the nucleic acid bases. Two such selection pressures may have been related to genetic fidelity and duplex stability. Considering these possible selection criteria, the native bases along with other related heterocycles seem to exhibit a certain level of fitness. We end by discussing the strength of the N-glycosidic bond as a potential fitness parameter in the early DNA world, which may have played a part in the refinement of the alphabetic bases.

Ocean oxygenation in the wake of the Marinoan glaciation

Metazoans are likely to have their roots in the Cryogenian period, but there is a marked increase in the appearance of novel animal and algae fossils shortly after the termination of the late Cryogenian (Marinoan) glaciation about 635 million years ago. It has been suggested that an oxygenation event in the wake of the severe Marinoan glaciation was the driving factor behind this early diversification of metazoans and the shift in ecosystem complexity. But there is little evidence for an increase in oceanic or atmospheric oxygen following the Marinoan glaciation, or for a direct link between early animal evolution and redox conditions in general. Models linking trends in early biological evolution to shifts in Earth system processes thus remain controversial. Here we report geochemical data from early Ediacaran organic-rich black shales (∼635-630 million years old) of the basal Doushantuo Formation in South China. High enrichments of molybdenum and vanadium and low pyrite sulphur isotope values (Δ(34)S values ≥65 per mil) in these shales record expansion of the oceanic inventory of redox-sensitive metals and the growth of the marine sulphate reservoir in response to a widely oxygenated ocean. The data provide evidence for an early Ediacaran oxygenation event, which pre-dates the previous estimates for post-Marinoan oxygenation by more than 50 million years. Our findings seem to support a link between the most severe glaciations in Earth's history, the oxygenation of the Earth's surface environments, and the earliest diversification of animals.

OLEB Executive Editors

With this issue, OLEB introduces a modified editorial structure. Two of our Editorial Board members, H.J. Cleaves and J. Peter Gogarten, will be assuming Executive Editor positions. Since its inception, Origins of Life has been a one-man operation, with, successively, Cyril Ponnamperuma, Jim Ferris, and myself as Editors. In today’s world of increasing specialization, it is becoming increasingly difficult for one editor to be sufficiently familiar with the entire breath of the journal’s coverage, or to easily identify and contact appropriate reviewers for every manuscript which is submitted. The new Executive Editors will act independently to stimulate, evaluate, and reach final decisions on new submissions within their areas of expertize. Jim Cleaves has a background in prebiotic chemistry, geochemistry and astrobiology. He is associated with the Geophysical Laboratory of the Carnegie Institution of Science, in Washington, D.C. Peter Gogarten is a specialist in Molecular and Early Biological Evolution, and is a Distinguished Professor in the Department of Molecular and Cell Biology at the University of Connecticut, Storrs, CT. I am delighted that I will be able to rely on their increased involvement in OLEB in the future. Orig Life Evol Biosph (2011) 41:397 DOI 10.1007/s11084-011-9245-2

Spontaneous chiral symmetry breaking in early molecular networks.

BackgroundAn important facet of early biological evolution is the selection of chiral enantiomers for molecules such as amino acids and sugars. The origin of this symmetry breaking is a long-standing question in molecular evolution. Previous models addressing this question include particular kinetic properties such as autocatalysis or negative cross catalysis.ResultsWe propose here a more general kinetic formalism for early enantioselection, based on our previously described Graded Autocatalysis Replication Domain (GARD) model for prebiotic evolution in molecular assemblies. This model is adapted here to the case of chiral molecules by applying symmetry constraints to mutual molecular recognition within the assembly. The ensuing dynamics shows spontaneous chiral symmetry breaking, with transitions towards stationary compositional states (composomes) enriched with one of the two enantiomers for some of the constituent molecule types. Furthermore, one or the other of the two antipodal compositional states of the assembly also shows time-dependent selection.ConclusionIt follows that chiral selection may be an emergent consequence of early catalytic molecular networks rather than a prerequisite for the initiation of primeval life processes. Elaborations of this model could help explain the prevalent chiral homogeneity in present-day living cells.ReviewersThis article was reviewed by Boris Rubinstein (nominated by Arcady Mushegian), Arcady Mushegian, Meir Lahav (nominated by Yitzhak Pilpel) and Sergei Maslov.

The origin of the biologically coded amino acids

Biology uses essentially 20 amino acids for its coded protein enzymes, representing a very small subset of the structurally possible set. Most models of the origin of life suggest organisms developed from environmentally available organic compounds. A variety of amino acids are easily produced under conditions which were believed to have existed on the primitive Earth or in the early solar nebula. The types of amino acids produced depend on the conditions which prevailed at the time of synthesis, which remain controversial. The selection of the biological set is likely due to chemical and early biological evolution acting on the environmentally available compounds based on their chemical properties. Once life arose, selection would have proceeded based on the functional utility of amino acids coupled with their accessibility by primitive metabolism and their compatibility with other biochemical processes. Some possible mechanisms by which the modern set of 20 amino acids was selected starting from prebiotic chemistry are discussed.

New species in evolving networks—stochastic theory of sensitive networks and applications on the metaphorical level

In this paper we develop a theory to describe stochastic influences on the fate of new species with non-linear growth rates in evolutionary processes. We develop a theoretical framework based on notions of species, network, innovation, competition, survival and fitness. We introduce a stochastic picture describing the role of fluctuations in the survival of new species in non-linear systems. In particular we consider the fate of new species with non-linear growth. As an application of the general model framework we consider the fate of ‘rare species’ in early biological evolution. We show that hypercycle systems do not represent the end of the evolutionary process as they may evolve further in small niches. This has implications for different types of applications ranging from biological systems on one level to socio-technological systems on a more metaphoric level.

Spherule beds 3.47-3.24 billion years old in the Barberton Greenstone Belt, South Africa: a record of large meteorite impacts and their influence on early crustal and biological evolution.

Four layers, S1-S4, containing sand-sized spherical particles formed as a result of large meteorite impacts, occur in 3.47-3.24 Ga rocks of the Barberton Greenstone Belt, South Africa. Ir levels in S3 and S4 locally equal or exceed chondritic values but in other sections are at or only slightly above background. Most spherules are inferred to have formed by condensation of impact-produced rock vapor clouds, although some may represent ballistically ejected liquid droplets. Extreme Ir abundances and heterogeneity may reflect element fractionation during spherule formation, hydraulic fractionation during deposition, and/or diagenetic and metasomatic processes. Deposition of S1, S2, and S3 was widely influenced by waves and/or currents interpreted to represent impact-generated tsunamis, and S1 and S2 show multiple graded layers indicating the passage of two or more wave trains. These tsunamis may have promoted mixing within a globally stratified ocean, enriching surface waters in nutrients for biological communities. S2 and S3 mark the transition from the 300-million-year-long Onverwacht stage of predominantly basaltic and komatiitic volcanism to the late orogenic stage of greenstone belt evolution, suggesting that regional and possibly global tectonic reorganization resulted from these large impacts. These beds provide the oldest known direct record of terrestrial impacts and an opportunity to explore their influence on early life, crust, ocean, and atmosphere. The apparent presence of impact clusters at 3.26-3.24 Ga and approximately 2.65-2.5 Ga suggests either spikes in impact rates during the Archean or that the entire Archean was characterized by terrestrial impact rates above those currently estimated from the lunar cratering record.

A Selected Ribozyme Catalyzing Diverse Dipeptide Synthesis

The sequence of events by which protein, RNA, and DNA emerged during early biological evolution is one of the most profound questions regarding the origin of life. The contemporary role of aminoacyl-adenylates as intermediates in both ribosomal and nonribosomal peptide synthesis suggests that they may have served as substrates for uncoded peptide synthesis during early evolution. We report a highly active peptidyl transferase ribozyme family, isolated by in vitro selection, that efficiently catalyzes dipeptide synthesis by using an aminoacyl-adenylate substrate. It was characterized by sequence and structural analysis and kinetic studies. Remarkably, the ribozyme catalyzed the formation of 30 different dipeptides, the majority of rates being within 5-fold that of the Met-Phe dipeptide required by the selection. The isolation of this synthetic ribozyme fosters speculation that ribozyme-mediated uncoded peptide synthesis may have preceded coded peptide synthesis.

Peptidyl-transferase ribozymes: trans reactions, structural characterization and ribosomal RNA-like features

Background: One of the most significant questions in understanding the origin of life concerns the order of appearance of DNA, RNA and protein during early biological evolution. If an ‘RNA world’ was a precursor to extant life, RNA must be able not only to catalyze RNA replication but also to direct peptide synthesis. Iterative Iterative RNA selection previously identified catalytic RNAs (ribozymes) that form amide bonds between RNA and an amino acid or between two amino acids. Results: We characterized peptidyl-transferase reactions catalyzed by two different families of ribozymes that use substrates that mimic A site and P site tRNAs. The family II ribozyme secondary structure was modeled using chemical modification, enzymatic digestion and mutational analysis. Two regions resemble the peptidyl-transferase region of 23S ribosomal RNA in sequence and structural context; these regions are important for peptide-bond formation. A shortened form of this ribozyme was engineered to catalyze intermolecular (‘ trans’) peptide-bond formation, with the two amino-acid substrates binding through an attached AMP or oligonucleotide moiety. Conclusions: An in vitro-selected ribozyme can catalyze the same type of peptide-bond formation as a ribosome; the ribozyme resembles the ribosome because a very specific RNA structure is required for substrate binding and catalysis, and both amino acids are attached to nucleotides. It is intriguing that, although there are many different possible peptidyl-transferase ribozymes, the sequence and secondary structure of one is strikingly similar to the ‘helical wheel’ portion of 23S rRNA implicated in ribosomal peptidyl-transferase activity.

Major “Anastrophes” in the Origin and Early Evolution of Biological Energy Conversion

The metabolism of living organisms has long been usefully divided into anabolism and catabolism. Anabolism is constructive, being concerned with the assembly of complex molecules, whereas catabolism is destructive in the sense that it involves the degradation of molecules. In addition to the well-known word catastrophe for sudden, drastic destruction and its consequences, it has been found practical to introduce in the evolutionary context the word “anastrophe” (an old greek word for turning back, in the opposite direction—from anastrephein, where ana=back and strephein=to turn) to cover sudden, drastic constructive events and their consequences.Mutations in genes and genomes giving selective advantage to an organism are typical anastrophic events. A single site mutation in a gene coding for a protein may be good, neutral or bad, or anastrophic, neutral or catastrophic, respectively, for the organism. The consequence of an anastrophic mutation may be a decisive first step on the long way to a new species, whereas a catastrophic mutation may lead to major cell damage or death. This example of the use of the anastrophe concept in biological evolution leads to the question about its applicability to other parts and paths of the cosmic evolutionary process, such as physical, chemical, social and cultural evolution. Here it will be mainly considered in connection with the energy conversion aspects of the chemical evolution leading to the origin of life and of the subsequent early biological evolution. More specifically, it will be attempted to describe possible major anastrophes in energy conversion both before and after the first occurrence of life on earth.

Secondary structural features of modules M2 and M3 of barnase in solution by NMR experiment and distance geometry calculation.

Proteins consist of structural units such as globular domains, secondary structures, and modules. Modules were originally defined by partitioning a globular domain into compact regions, each of which is a contiguous polypeptide segment having a compact conformation. Since modules show close correlations with the intron positions of genes, they are regarded as primordial polypeptide pieces encoded by exons and shuffled, leading to yield new combination of them in early biological evolution. Do modules maintain their native conformations in solution when they are excised at their boundaries? In order to find answers to this question, we have synthesized modules of barnase, one of the bacterial RNases, and studied the solution structures of modules M2 (amino acid residues 24-52) and M3 (52-73) by 2D NMR studies. Some local secondary structures, alpha-helix, and beta-turns in M2 and beta-turns in M3, were observed in the modules at the similar positions to those in the intact barnase but the overall state seems to be in a mixture of random and native conformations. The present result shows that the excised modules have propensity to form similar secondary structures to those of the intact barnase.

General discussion after session V

N. C. Wickramasinghe ( Department of Applied Mathematics and Astronomy, University College, Cardiff, U. K. ). The question of the origin of life is, of course, one of the most important scientific questions and it is also one of the most difficult. One is inevitably faced here with a situation where there are very few empirical facts of direct relevance and perhaps no facts relating to the actual transition from organic material to material that can even remotely be described as living. The time perspective of events that relate to this problem has already been presented by Dr Chang. Uncertainty still persists as to the actual first moment of the origin or the emergence of life on the Earth. At some time between 3800 and 3300 Ma BP the first microscopic living systems seem to have emerged. There is a definite moment in time corresponding to a sudden appearance of cellular-type living systems. Now, traditionally the evolution of carbonaceous compounds which led to the emergence of life on Earth could be divided into three principal steps and I shall just remind you what those steps are. The first step is the production of chemical building blocks that lead to the origin of the organic molecules necessary as a prerequisite for the evolution of life. Step two can be described in general terms as prebiotic evolution, the arrangement of these chemical units into some kind of sequence of precursor systems that come almost up to life but not quite; and then stage three is the early biological evolution which actually effects the transition from proto-cellular organic-type forms into truly cellular living systems. The transition is from organic chemistry, prebiotic chemistry to biochemistry. Those are the three principal stages that have been defined by traditional workers in the field, the people who, as Dr Chang said, have had the courage to make these queries and attempt to answer them. Ever since the classic experiments where organic materials were synthesized in the laboratory a few decades back, it was thought that the first step, the production of organic chemical units, is important for the origin of life on the Earth, and that this had to take place in some location on the Earth itself.

Interaction, functional relations and evolution of large and small subunits in Rubisco from prokaryota and eukaryota.

In early biological evolution anoxygenic photosynthetic bacteria may have been established through the acquisition of ribulose bisphosphate carboxylase-oxygenase (Rubisco). The establishment of cyanobacteria may have followed and led to the production of atmospheric oxygen. It has been postulated that a unicellular cyanobacterium evolved to cyanelles which were evolutionary precursors of chloroplasts of both green and non-green algae. The latter probably diverged from ancestors of green algae as evidenced by the occurrence of large (L) and small (S) subunit genes for Rubisco in the chloroplast genome of the chromophytic algae Olisthodiscus luteus. In contrast, the gene for the S subunit was integrated into the nucleus in the evolution of green algae and higher plants. The evolutionary advantages of this integration are uncertain because the function of S subunits is unknown. Recently, two forms of Rubisco (L8 and L8S8) of almost equivalent carboxylase and oxygenase activity have been isolated from the photosynthetic bacterium Chromatium vinosum. This observation perpetuates the enigma of S subunit function. Current breakthroughs are imminent, however, in our understanding of the function of catalytic L subunits because of the application of deoxyoligonucleotide-directed mutagenesis. Especially interesting mutated Rubisco molecules may have either enhanced carboxylase activity or higher carboxylase:oxygenase ratios. Tests of expression, however, must await the insertion of modified genes into the nucleus and chloroplasts. Methodology to accomplish chloroplast transformation is as yet unavailable. Recently, we have obtained the first transformation of cyanobacteria by a colE1 plasmid. We regard this transformation as an appropriate model for chloroplast transformation.

The Evolution of Culture in Animals

Animals do have culture, maintains this delightfully illustrated and provocative book, which cites a number of fascinating instances of animal communication and learning. John Bonner traces the origins of culture back to the early biological evolution of animals and provides examples of five categories of behavior leading to nonhuman culture: physical dexterity, relations with other species, auditory communication within a species, geographic locations, and inventions or innovations. Defining culture as the transmission of information by behavioral rather than genetical means, he demonstrates the continuum between the traits we find in animals and those we often consider uniquely human.

TITMICE, SLIME MOLDS, AND CULTURAL EVOLUTION

It is hard to visit England these days without coming face to face with the realities of animal culture as defined by J. T. Bonner. A well-skimmed bottle of milk is the penalty for failing to take proper precautions against marauding titmice, who peck open the foil caps and drink the cream off the top. Local milkmen claim that the titmice have lately become rather refined. When they steal from open milk trucks, they limit their thieving almost entirely to the extra rich milk with the gold foil caps and leave the normal, silver capped milk alone. The spread of this milk robbing behavior in the titmouse population of Britain is a famous case of the transfer of information by behavioral means, and this is how Bonner defines culture. Increased attention to cultural transmission in animals is a natural and welcome response to the strong emphasis on genetic mechanisms in current sociobiology. It is a response that seems overdue. Undoubtedly, the delay was caused by some of the same factors that Griffin (1977) has postulated for the widespread reluctance of behavioral scientists to investigate the question of animal awareness-namely, difficult methodological problems and a strong tradition of thinking of animals as machines. This could explain why, as Bonner points out, there has been so little work on teaching in animals, though it is clear that teaching occurs. The Evolution of Culture in Animals is aimed at a surprisingly wide audience. Bonner wants to reach professional biologists, social scientists, and wellread lay people. His purpose is . . to trace the origins of the human cultural capacity back into early biological evolution. The book is not a review of the literature but a statement of a point of view, illustrated with a wide variety of examples. Bonner wishes to demonstrate the usefulness of treating culture as a multifaceted phenomenon, elements of which can be found in many animal groups. The bulk of the book is devoted to an examination of the principal components of the capacity for culture, the degree to which they occur in various animal groups, and a discussion of several examples of culture in animals. Bonner's first component is a capacity for fast behavioral responses, which can be seen, of course, even in bacteria. The next step is the development of a central nervous system capable of a large amount of information processing. This