1

Evoluzione orizzontale e ontologia biologica

Emanuele SerrelliPadova, 8-9 maggio 2012

emanuele.serrelli@unimib.it

http://www.epistemologia.eu

2

Selves

Groups

Earth

Chimeras

Consciousness

3

Selves

4

. . .the “selves” of viruses, utterly depend on their physical contact with bacterial or other living cells. If

not connected to a cell, a virus is as inert as a lump of salt or a cube of sugar. The basic element of life, the

self, is the sensitive bacterial cell; but a virus, as a courier and an integrator of genes into bacteria and

nucleated organisms (animals, plants, fungi and proctotists), can be very important to specific

evolutionary trajectories.(William Day, ch. 2, p. 17)

Selveshttp://jonlieffmd.com/blog/are-viruses-alive-are-viruses-sentient-virus-intelligence

5

Selves

http://microbes.nres.uiuc.edu/NRES512.htm

Rymer et al. (2012)

6

Selves

http://microbes.nres.uiuc.edu/NRES512.htm

http://microbes.nres.uiuc.edu/NRES512.htm

7

Groups

Ben Jacob et al. (2004)

8

Groups

Bressan (2012)

Groups

9

Murray Bowen photo by Andrea Maloney Schara (1979)http://ideastoaction.wordpress.com/2012/08/29/murray-bowen/

10

11

Chimeras

Chimera di Arezzo, Museo Archeologico, Firenze

Chimeras

12

Vad Drisse (2011)

Chimeras

12

Vad Drisse (2011)

Margulis et al. (2006)

Chimeras

13

Invertebrates...

http://in2uract.wordpress.com/2011/11/24/strengthening-your-immune-system/

Chimeras

14Alves et al.

LemurFamily: Galagidae

http://collections.burkemuseum.org/mtm/images/mtm_slideshows/

3027712362_de1ae16a96_o.jpg

Chimeras

15

Chimeras

16

http://neurosciencefundamentals.unsw.wikispaces.net/The+Neurons+that+Shaped+Our+Worldhttp://www.ted.com/talks/vs_ramachandran_the_neurons_that_shaped_civilization.html

Consciousness

17

LemurFamily: Galagidae

http://collections.burkemuseum.org/mtm/images/mtm_slideshows/

3027712362_de1ae16a96_o.jpg

George Mobushttp://faculty.washington.edu/gmobus/Background/evolutionsTrajectory.html

Consciousness

18http://thecampbellgrp.com/glonal-network/

19

Selves

Groups

Earth

Chimeras

Consciousness

20

21

http://evolutionschool.fc.ul.pt

22

For there is, after all, one true tree of life, the unique pattern of evolutionary branchings that

actually happened. It exists. It is in principle knowable. We don’t know it all yet. By 2050 we

should—or if we do not, we shall have been defeated only at the terminal twigs, by the sheer

number of species. ... [H]undreds of separate genes ... are found to corroborate each other’s accounts of the one true tree of life (Dawkins

2003, p. 112; see also Eldredge 2005, p. 227).

23

http://edge.org/conversation/lynn-margulis1938-2011

SET - Serial Endosymbiosis Theory for the origin of eukaryotic cells

24

http://img.scoop.co.nz/stories/images/0903/a8de5c88b14851860daa.jpeg

Image courtesy of Lynn Margulis

25http://img.scoop.co.nz/stories/images/0903/a8de5c88b14851860daa.jpeg

Image courtesy of Lynn Margulis

26

26

27

Virolution at the pro- and eukaryotic level Villarreal & Ryan

28

1957Molecular phylogen.

SSU rRNA (Woese)

19871990s on 2004

29W. Ford Doolittle

1957

In the case of higher plants and animals, species can be grouped into genera, families, and orders on the

basis of their evolutionary relationships, or phylogeny. Such classifications are called natural classifications. In

the bacteria, however, only a few broad lines of evolution are dimly perceivable, and the finer details of

phylogeny remain completely obscure. The existing semiofficial classification of bacteria, Bergey’s Manual, is thus an arbitrary one, and is useful only to the limited

extent that it serves as a ‘‘key’’ for identification.(Steiner et al. 1957)

Phylogeny of bacteria

30W. Ford Doolittle

1957

Phylogeny of bacteria

Molecular phylogen.

phylogenies based on the sequences of ‘‘informational macromolecules’’ are not only more unambiguously

quantifiable but closer to what it is that actually evolves—genes and the genome.

...extend the universal Tree of Life downward to its deepest roots among the prokaryotes

31W. Ford Doolittle

1957

Phylogeny of bacteria

Molecular phylogen.

SSU rRNA (Woese)

32W. Ford Doolittle

1957

Phylogeny of bacteria

Molecular phylogen.

SSU rRNA (Woese)

Lateral, Horizontal gene transfer at the prokaryotic level:

gene donations of bacteria: e.g. resistance of bacteria against antibiotics

32W. Ford Doolittle

1957

Phylogeny of bacteria

Molecular phylogen.

SSU rRNA (Woese)

Lateral, Horizontal gene transfer at the prokaryotic level:

gene donations of bacteria: e.g. resistance of bacteria against antibiotics

...microbiologists had uncovered a phenomenon that might have given them cause to worry that the

evolution of genes might not always be tree-like, and that gene trees might not always be species trees.

33W. Ford Doolittle

1957

Phylogeny of bacteria

Molecular phylogen.

SSU rRNA (Woese)Why few of us thought that LGT would

interfere seriously with universal tree construction is an interesting question for

the historian and sociologist...

34W. Ford Doolittle

1957

Phylogeny of bacteria

Molecular phylogen.

SSU rRNA (Woese)

1987

In the extreme, interspecies exchanges of genes could be so rampant, so broadspread, that a bacterium would not actually have a history in its own right; it would be an evolutionary chimera, a

collection of genes (or gene clusters), each with its own

history...

35W. Ford Doolittle

1957

Phylogeny of bacteria

Molecular phylogen.

SSU rRNA (Woese)

1987

Fortunately the matter is experimentally decidable.

Were an organism an evolutionary chimera, then its various chronometers would yield different, conflicting

phylogenies.

36W. Ford Doolittle

1957

Phylogeny of bacteria

Molecular phylogen.

SSU rRNA (Woese)

19871990s on

37W. Ford Doolittle

1957

Phylogeny of bacteria

Molecular phylogen.

SSU rRNA (Woese)

19871990s on

Assessing how many of a genomes’ genes have been laterally transferred at some time in its history will always be technically difficult and fraught with definitional problems, although few would now claim that the fraction is less than

one half, and many would accept that it is more than 95%. It turns out to be simpler to ask how many and which genes might possibly have

avoided LGT in the last four billion years.

38W. Ford Doolittle

1957

Phylogeny of bacteria

Molecular phylogen.

SSU rRNA (Woese)

19871990s on

39W. Ford Doolittle

1957

Phylogeny of bacteria

Molecular phylogen.

SSU rRNA (Woese)

19871990s on

40

Network diagrams combines both horizontal and vertical evolutionary events in prokaryotes Dagan and Martin, 2009: 2190

41

Margulis

Symbiogenesis

1957Molecular phylogen.

SSU rRNA (Woese)

19871990s on

42

Margulis

Symbiogenesis

1957Molecular phylogen.

SSU rRNA (Woese)

19871990s on

Symbiogenesis

43

http://img.scoop.co.nz/stories/images/0903/a8de5c88b14851860daa.jpeg

Image courtesy of Lynn Margulis

44

Margulis

Symbiogenesis

1957Molecular phylogen.

SSU rRNA (Woese)

19871990s on

Original formulation of symbiosis theory

by Constantin Mereschkowsky

1909

45

How many individuals ? How many kinds of individuals?

19

We need better definitions of individuals

Courtesy of Fred Bouchhard, 2013

46

MaureenO’Malley

Centrality of Biological species and their tree

1957Molecular phylogen.

SSU rRNA (Woese)

19871990s on

Ernst Mayr, the tree of life, and philosophy of biology

Maureen A. O’Malley

Published online: 8 May 2010! Springer Science+Business Media B.V. 2010

Abstract Ernst Mayr’s influence on philosophy of biology has given the field aparticular perspective on evolution, phylogeny and life in general. Using debatesabout the tree of life as a guide, I show how Mayrian evolutionary biology excludesnumerous forms of life and many important evolutionary processes. Hybridizationand lateral gene transfer are two of these processes, and they occur frequently, withimportant outcomes in all domains of life. Eukaryotes appear to have a more tree-like history because successful lateral events tend to occur among more closelyrelated species, or at a lower frequency, than in prokaryotes, but this is a differenceof degree rather than kind. Although the tree of life is especially problematic as arepresentation of the evolutionary history of prokaryotes, it can function moregenerally as an illustration of the limitations of a standard evolutionary perspective.Moreover, for philosophers, questions about the tree of life can be applied to theMayrian inheritance in philosophy of biology. These questions make clear that thedichotomy of life Mayr suggested is based on too narrow a perspective. An alter-native to this dichotomy is a multidimensional continuum in which differentstrategies of genetic exchange bestow greater adaptiveness and evolvability on pro-karyotes and eukaryotes.

Keywords Ernst Mayr ! Philosophy of biology ! Evolution ! Tree of life !Species ! Lateral gene transfer ! Hybridization

Introduction

Most philosophers of biology have in the back of their mind at least a vague image ofa tree of life that depicts bifurcating species lineages and represents the evolutionary

M. A. O’Malley (&)Egenis, University of Exeter, St Germans Road, EX4 4PJ Exeter, UKe-mail: M.A.O’Malley@ex.ac.uk

123

Biol Philos (2010) 25:529–552DOI 10.1007/s10539-010-9214-6

47

MaureenO’Malley

Centrality of Biological species and their tree

1957Molecular phylogen.

SSU rRNA (Woese)

19871990s on 2004

All so-called asexually reproducing organisms do not have species.

The prokaryotes are difficult enough [to deal with], but even

when you get into the low eukaryotes, there is this group that is a sort of a garbage can called the protists. And there are authors I’m told that recognize 80 phyla of protists. God knows what there is

in these 80 phyla. And most of them do not have species in the normal sense. They don’t have a proper process of speciation or

anything like that.

48But again, on the pragmatic grounds of removing the messier, more web-like

evolutionary patterns such processes produce, we could conclude that Mayr isjustified in excluding protists (along with prokaryotes) for not having reproductivelyisolated species. Representations of evolution would have to encompass multipleprocesses and entities, and trees would become very difficult to construct ifdisorderly organisms were to be admitted. But if evolutionary systematists arewilling to discard protists, the same logic that allows this exclusion will have toallow the omission of even more eukaryotes from mainstream evolutionaryunderstanding.

Fungi

Fungi are highly diverse and prolific entities, ranging from single-celled organisms(e.g. yeast, moulds) to gigantic clones many hectares in dimension (Smith et al.1992; Bendel et al. 2006). The full extent of their diversity is still unknown, but it isthought to be at the level of insects (Hawksworth 2001; McLaughlin et al. 2009).Mayr tended to ignore fungi or to lump them into discussions of protists, eventhough he was impressed by the fact that fungi were eventually recognized as closerto animals than plants (1998b). His lack of attention to them was probably due to the

Fig. 1 Six eukaryote supergroups. Reprinted from Lane and Archibald (2008), with permission fromElsevier

538 M. A. O’Malley

123

From Lane and Archibald (2008), in O’Malley 2010

MaureenO’Malley

there is growing evidence of gene exchange in protists (Keeling and Palmer 2008; Andersson 2009). Sequence analyses of several protist genomes have detected bacterial genes in varying amounts, with as

much as 4% of rumen ciliate genomes being of foreign origin (Ricard et al. 2006). In the genome of the miniscule green alga, Ostreococcus tauri, the

smallest free-living eukaryote, a whole chromosome appears to have been acquired, although its source is not obvious (Derelle et al. 2006). The

pathogens Giardia lamblia, Trichomonas vaginalis, and Entamoeba histolytica have ‘borrowed’ large numbers of virulence and metabolism genes from bacteria (Andersson et al. 2006; Loftus et al. 2005). Transfers between protists, and from other eukaryotes to protists, have also been found in increasing numbers, and the data for such acquisitions increase with every genome sequence deposited in GenBank or other databases (Andersson 2009). The more lateral gene transfer in protists is studied, in fact, the more that is learned about interdomain exchange as an ongoing

evolutionary mechanism of genetic diversity (Andersson et al. 2006).

48But again, on the pragmatic grounds of removing the messier, more web-like

evolutionary patterns such processes produce, we could conclude that Mayr isjustified in excluding protists (along with prokaryotes) for not having reproductivelyisolated species. Representations of evolution would have to encompass multipleprocesses and entities, and trees would become very difficult to construct ifdisorderly organisms were to be admitted. But if evolutionary systematists arewilling to discard protists, the same logic that allows this exclusion will have toallow the omission of even more eukaryotes from mainstream evolutionaryunderstanding.

Fungi

Fungi are highly diverse and prolific entities, ranging from single-celled organisms(e.g. yeast, moulds) to gigantic clones many hectares in dimension (Smith et al.1992; Bendel et al. 2006). The full extent of their diversity is still unknown, but it isthought to be at the level of insects (Hawksworth 2001; McLaughlin et al. 2009).Mayr tended to ignore fungi or to lump them into discussions of protists, eventhough he was impressed by the fact that fungi were eventually recognized as closerto animals than plants (1998b). His lack of attention to them was probably due to the

Fig. 1 Six eukaryote supergroups. Reprinted from Lane and Archibald (2008), with permission fromElsevier

538 M. A. O’Malley

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From Lane and Archibald (2008), in O’Malley 2010

MaureenO’Malley

49But again, on the pragmatic grounds of removing the messier, more web-like

evolutionary patterns such processes produce, we could conclude that Mayr isjustified in excluding protists (along with prokaryotes) for not having reproductivelyisolated species. Representations of evolution would have to encompass multipleprocesses and entities, and trees would become very difficult to construct ifdisorderly organisms were to be admitted. But if evolutionary systematists arewilling to discard protists, the same logic that allows this exclusion will have toallow the omission of even more eukaryotes from mainstream evolutionaryunderstanding.

Fungi

Fungi are highly diverse and prolific entities, ranging from single-celled organisms(e.g. yeast, moulds) to gigantic clones many hectares in dimension (Smith et al.1992; Bendel et al. 2006). The full extent of their diversity is still unknown, but it isthought to be at the level of insects (Hawksworth 2001; McLaughlin et al. 2009).Mayr tended to ignore fungi or to lump them into discussions of protists, eventhough he was impressed by the fact that fungi were eventually recognized as closerto animals than plants (1998b). His lack of attention to them was probably due to the

Fig. 1 Six eukaryote supergroups. Reprinted from Lane and Archibald (2008), with permission fromElsevier

538 M. A. O’Malley

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From Lane and Archibald (2008), in O’Malley 2010

MaureenO’Malley

In fungi, there is a growing list of what seem to be fungal hybrids (Schardl and Craven 2003; Novo et al. 2009). Moreover, there appears to be a great deal of LGT occurring between prokaryotes and fungi, between

fungal lineages, and between fungi and other multicellular eukaryotes (e.g. Schardl and Craven 2003; Friesen et al. 2006; Richards et al. 2006,

2009). Numerous phylogenetically discordant plasmids, transposons and gene clusters have been detected in a range of fungal lineages, and even

some whole chromosome transfers between filamentous fungi (Walton 2000). In addition, there is good experimental evidence of

transformation (uptake of environmental DNA) in a few fungi (Rosewich and Kistler 2000). Whether novel DNA is acquired by hybridization or by LGT, it has either to be excluded from phylogenetic analysis or depicted

as a reticulate event.

50But again, on the pragmatic grounds of removing the messier, more web-like

evolutionary patterns such processes produce, we could conclude that Mayr isjustified in excluding protists (along with prokaryotes) for not having reproductivelyisolated species. Representations of evolution would have to encompass multipleprocesses and entities, and trees would become very difficult to construct ifdisorderly organisms were to be admitted. But if evolutionary systematists arewilling to discard protists, the same logic that allows this exclusion will have toallow the omission of even more eukaryotes from mainstream evolutionaryunderstanding.

Fungi

Fungi are highly diverse and prolific entities, ranging from single-celled organisms(e.g. yeast, moulds) to gigantic clones many hectares in dimension (Smith et al.1992; Bendel et al. 2006). The full extent of their diversity is still unknown, but it isthought to be at the level of insects (Hawksworth 2001; McLaughlin et al. 2009).Mayr tended to ignore fungi or to lump them into discussions of protists, eventhough he was impressed by the fact that fungi were eventually recognized as closerto animals than plants (1998b). His lack of attention to them was probably due to the

Fig. 1 Six eukaryote supergroups. Reprinted from Lane and Archibald (2008), with permission fromElsevier

538 M. A. O’Malley

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From Lane and Archibald (2008), in O’Malley 2010

MaureenO’Malley

They can combine sexual and asexual reproduction (with sexual reproduction being the ancient state, since lost in many lineages), and it is

still sometimes unclear how particular fungi reproduce (Petersen and Hughes 1999; Schardl and Craven 2003; Zeyl 2009). One reproductive

peculiarity of fungi involves hyphal fusion, in which fungal filaments anastomose parasexually, through somatic recombination rather than

germ cell recombination. Large numbers of nuclei (sometimes thousands) from the different hyphae share the same enlarged cell compartment. In many lineages, interspecific matings are vegetatively incompatible, which means that the non-self recognition of introduced genetic systems results in the destruction of the newly merged hyphal cells (Glass and Dementhon 2006; Glass and Kaneko 2003; Giraud et al. 2008). Even when this does

not happen, the heterokaryon products of hyphal fusion (cells with different genotypes) may be unstable and produce only homokaryotic offspring. But this is not always the case, and nor does incompatibility

recognition happen for all hyphal fungi.

51But again, on the pragmatic grounds of removing the messier, more web-like

evolutionary patterns such processes produce, we could conclude that Mayr isjustified in excluding protists (along with prokaryotes) for not having reproductivelyisolated species. Representations of evolution would have to encompass multipleprocesses and entities, and trees would become very difficult to construct ifdisorderly organisms were to be admitted. But if evolutionary systematists arewilling to discard protists, the same logic that allows this exclusion will have toallow the omission of even more eukaryotes from mainstream evolutionaryunderstanding.

Fungi

Fungi are highly diverse and prolific entities, ranging from single-celled organisms(e.g. yeast, moulds) to gigantic clones many hectares in dimension (Smith et al.1992; Bendel et al. 2006). The full extent of their diversity is still unknown, but it isthought to be at the level of insects (Hawksworth 2001; McLaughlin et al. 2009).Mayr tended to ignore fungi or to lump them into discussions of protists, eventhough he was impressed by the fact that fungi were eventually recognized as closerto animals than plants (1998b). His lack of attention to them was probably due to the

Fig. 1 Six eukaryote supergroups. Reprinted from Lane and Archibald (2008), with permission fromElsevier

538 M. A. O’Malley

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From Lane and Archibald (2008), in O’Malley 2010

MaureenO’Malley

study after study has documented the adaptiveness and proliferation of plant hybrids (Heiser 1973; Arnold 2006; Arnold et al. 1999; Soltis and

Soltis 2009). Much known hybridization involves genome doubling (allopolyploidy), which has played a major role in plant evolution (Adams

and Wendel 2005). Other hybridization events involve genome recombination (homoploidy). An example of the latter, which is more

difficult to detect, is provided by the sunflowers Helianthus annuus and H. petiolaris. These parental species have three hybrid offspring (H.

anomalus, H. deserticola, and H. paradoxus) that evolved between 60,000 and 200,000 years ago. While the parent plants favour temperate climates, the hybrid offspring inhabit and flourish in extreme environments,

such as harsh desert conditions and salt marshes (Rieseberg 1997; Rieseberg et al. 2003). It is frequently the case that hybrid offspring have hardier characteristics than their parents, due to new gene combinations that allow the hybrids to colonize new ecological niches (Rieseberg and

Willis 2007).

52But again, on the pragmatic grounds of removing the messier, more web-like

evolutionary patterns such processes produce, we could conclude that Mayr isjustified in excluding protists (along with prokaryotes) for not having reproductivelyisolated species. Representations of evolution would have to encompass multipleprocesses and entities, and trees would become very difficult to construct ifdisorderly organisms were to be admitted. But if evolutionary systematists arewilling to discard protists, the same logic that allows this exclusion will have toallow the omission of even more eukaryotes from mainstream evolutionaryunderstanding.

Fungi

Fungi are highly diverse and prolific entities, ranging from single-celled organisms(e.g. yeast, moulds) to gigantic clones many hectares in dimension (Smith et al.1992; Bendel et al. 2006). The full extent of their diversity is still unknown, but it isthought to be at the level of insects (Hawksworth 2001; McLaughlin et al. 2009).Mayr tended to ignore fungi or to lump them into discussions of protists, eventhough he was impressed by the fact that fungi were eventually recognized as closerto animals than plants (1998b). His lack of attention to them was probably due to the

Fig. 1 Six eukaryote supergroups. Reprinted from Lane and Archibald (2008), with permission fromElsevier

538 M. A. O’Malley

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From Lane and Archibald (2008), in O’Malley 2010

MaureenO’Malley

One classic study that did not quite fit Mayr’s expectations was carried out by Lewontin and L. C. Birch (1966). They argued that hybridization was a source of

variation for adaptation to new environments in particular groups of Queensland fruit flies (then Dacus, now Bactrocera tryoni and B. neohumeralis)...

...because hybridization is usually investigated in relation to visibly distinguishable taxa, it has probably been systematically underestimated in duller, more uniform types of organisms such as little brown birds or butterflies (Mallet 2005; Dowling and Secor

1997). Some classic examples include ducks (much collected during hunting seasons, and therefore well observed), birds of paradise, cichlids and butterflies

(see Mallet et al. 2007). Cichlids and other freshwater fish are well known for their hybridization capacities, partly because of the very divergent morphologies and colour

patterns produced by introgression (Koblmüller et al. 2007). In representing these introgressions phylogenetically, many branches have to be reticulated to make sense

of incongruent gene phylogenies.Although there may be low levels of fertility in the first generation of hybrids, later

generations frequently stabilize, often with fitness advantages in new or expanded environments (Anderson 1948; Arnold 2006). And although rates of hybridization may be low, they can have major evolutionary consequences (Seehausen 2004; Dowling

and Secor 1997).

53

Virolution at the pro- and eukaryotic level Villarreal & Ryan

53

Virolution at the pro- and eukaryotic level Villarreal & Ryan

Much of the known LGT in animals involves acquisitions from prokaryotes, such as genes for cellulose biosynthesis in marine invertebrates, and glyoxylate-cycle enzymes in a number of animals (Nakashima et al. 2004; Kondrashov et al. 2006).

The genomes of Wolbachia-infected insects can carry large fragments of Wolbachia DNA— nearly a whole Wolbachia genome in one case (Hotopp et al.

2007).An even more intriguing example of animal LGT is that of bdelloid rotifers (a

microscopic multicellular aquatic animal), the genomes of which show evidence of recent and ancient acquisitions of bacterial, fungal, and plant genes (Gladyshev et al. 2008). Rotifers have a life cycle that can include dessication, and as the dessicated

body revives in the presence of water, environmental DNA seems to be integrated into the rotifer’s genome through a combination of membrane damage and DNA repair

mechanisms, and then inherited in the absence of sexual recombination. Most of the intact foreign genes code for simple enzymatic functions such as carbohydrate

decomposition (rather than multi- component biochemical pathways)...Some plant-parasitic nematodes have acquired bacterial genes that enable the

nematodes to modify plant cell walls, thereby damaging the plant but nourishing the nematode (Scholl et al. 2003).

54

MaureenO’Malley

Centrality of Biological species and their tree

1957Molecular phylogen.

SSU rRNA (Woese)

19871990s on 2004

55

HybridizationSchwenk et al. (2008)

56

Hybridization

1957Molecular phylogen.

SSU rRNA (Woese)

19871990s on 2004

57

Animal (and plant) evolution Representative Well represented

by tree Impact on TOL

Mayr Yes Yes -

Doolittle No Yes Circumscribe

Margulis No No Replace

O’Malley No No Multidimensional space

Hybrid. studies N/A (yes) Yes Speciation and adaptation mech.

58

Animal (and plant) evolution Representative Well represented

by tree Impact on TOL

Mayr Yes Yes -

Doolittle No Yes Circumscribe

Margulis No No Replace

O’Malley No No Multidimensional space

Hybrid. studies N/A (yes) Yes Speciation and adaptation mech.

58

evolution of multicellular animals and plants can still be

well understood as a branching process (albeit with some

fuzziness)

prokaryotic evolution may be better modeled as a reticulated web. This is because prokaryotes (bacteria and

archaea) much more readily exchange genes ‘‘across species lines’’, by several genetic mechanisms collectively known

as lateral gene transfer (LGT). Since prokaryotes comprise the majority of living things, and since the first two-thirds of Life’s history is exclusively prokaryotic, the TOL is of limited

explanatory scope.

59

Animal (and plant) evolution Representative Well represented

by tree Impact on TOL

Mayr Yes Yes -

Doolittle No Yes Circumscribe

Margulis No No Replace

O’Malley No No Multidimensional space

Hybrid. studies N/A (yes) Yes Speciation and adaptation mech.

A key residual question from the discussion above is whether evolutionary biology and its philosophy should follow

Mayr and split evolution into two types: the processes and outcomes that occur with ‘good’ speciators, and those that occur

with ‘bad’ speciators...a continuum perspective is the only

remaining optionmultiple intersecting continua: asexual-

sexual, much-less-exchange, uni-multicellular...

an approach along these lines would be more informative than a focus on which organisms have evolved in tree-like patterns. A

multidimensional approach by no means rejects the importance of such patterns, nor of the processes that gave rise to them, but it sees them as just one possible focus and not always the most

valuable one.

?

References

62

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• Debernardi M, Serrelli E (2013). From bacteria to Saint Francis to Gaia in the symbiotic view of evolution. Evolution: Education and Outreach 6(4). ISSN 1936-6426 (Print), 1936-6434 (Online) [DOI 10.1186/1936-6434-6-4]

• Ford Doolittle, W., 2010. The attempt on the life of the Tree of Life: science, philosophy and politics. Biology & Philosophy, 25(4), pp.455–473.

• Margulis L (1995). Gaia is a tough bitch. In John Brockman, ed. The Third Culture: Beyond the Scientific Revolution. New York: Simon & Schuster, pp. 130-140.

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• O’Malley, MA. (Ed.) (2010). Special issue on the tree of life (15 papers). Biology and Philosophy, 25(4).

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• Richard U. Rymer RU, Solorio FA, Tehranchi AK, Chu C, Corn JE, Keck JL, Wang JD, Berger JM (2012). Binding mechanism of metal⋅NTP substrates and stringent-response alarmones to bacterial DnaG-Type primases. Structure 20(9): 1478-1489.

• Sagan, L., 1967. On the origin of mitosing cells. Journal of theoretical biology, 14(3), pp.255–74.

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