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Human Evolution > Species concept > Flashcards

Species concept Flashcards

1
Q

Give a living example of how species is unclear

What would the biological and ecological species concept argue

A

o Baboons
 Are P. Anubis and P. hamadryas 1 or 2 species?
 Biological species concept – can interbreed to produce fertile offspring (eg donkey and horse to make mule)
 Anubis and hamadyras can interbreed and produce a fertile hybrid
• Therefore BSC suggests they are 1 species
 Ecological species concept = group of organisms that share the same ecological niche (environment, habitat etc)
• Hamadryas have very different niche to olive baboon (see slide)
• ESC suggests different species

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2
Q

Are hamadryas and olive baboons the same species

use the genetic, phylogenetic, and evolutionary species concepts

A

 Genetic species concept = group of genetically compatible organisms that are genetically isolated from other groups
• Olive and hamadryas are not genetically isolated therefore GSC suggests they are the same species

 Phylogenetic species concept = lineages diagnosable by a unique combination of character states (ie phenotype)

 Evolutionary species concept = lineage evolving separately from others with its own evolutionary role and tendencies

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3
Q

What is the biological species concept

A

a group of organisms that are capable of interbreeding with one another in nature and produce fertile offspring (Mayr, 1942).

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4
Q

What is the ecological species concept

A

a group of organisms that share the same ecological niche (i.e., interactions with the ecosystem).

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5
Q

How do the ecological niches of hamadryas vs olive baboons compare

A

hamadryas =

  • arid habitats
  • one male-units
  • interactions regardless the females’ reproductive state
olive==
- rainforests
- multimale and multifemale groups
- interactions limited to the
females’ receptive periods
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6
Q

What is the genetic species concept

A

group of genetically compatible organisms genetically isolated from other groups (genetic isolation ≠ reproductive isolation).

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7
Q

What is the phylogenetic species concept

A

populations or lineages diagnosable by a unique combination of character states (Cracraft, 1983).

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8
Q

What would the phylogenetic species concept say of the olive vs hamadryas baboons

A
  • gray-brown
  • medium skull
  • normal postorbital constriction
  • anteriorly placed temporal line
  • olive-brown
  • medium-large skull
  • normal postorbital constriction
  • normal temporal line

two species

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9
Q

What is the evolutionary species concept

A

a lineage evolving separately from the others with its own evolutionary role and tendencies (Simpson, 1951).

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10
Q

Which species concepts are applicable to fossils

A
  • Phylogenetic species concept lineage

* Evolutionary species concept diagnosis

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11
Q

Which species concepts are not applicable to fossils

A

 BSC: hard to know if fossil species could interbreed
 GSC: we can only do this when we can extract DNA
 ESC: hard to know social side of extinct species

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12
Q

What is the most important species diagnosis in fossils

A

In absence of soft tissues and molecular data, we have to rely on morphological
characters.
• Apomorphy (derived): evolutionary change.
• Autapomorphy: derived character confined in one taxon.
≠
• Plesiomorphy (ancestral): character retained from the ancestor.

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13
Q

What is a key problem with the fossil record when diagnosing species

A

• Variation
o Observable differences in the phenotype of specimens included in the same taxonomical, chronological, geographical or morphological unit.
o How does it differ from diversity
o Polymorphism
 the occurrence of different forms among the members of a population or colony

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14
Q

What are different types of intraspecies variation

When does variation become interspecific

A

sexual dimorphism

ontogeny

geography

pathologies

time (diachronic changes)

variation should exceed intra-specific variation observed in extant species

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15
Q

How did the biological community decide Homo luzonensis was a different species from floresiensis

A

o performed between group principle component analysis and found there is a big difference from other groups suggesting it is a new species based on this one factor
 using one specific character – enamel-dentine junction
 very big variation

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16
Q

Give an example of sexual dimorphism being used to explore intraspecies variation

A

Lufengpithecus: one single dimorphic taxon?

Kelley & Qinghua (1991) found that L. lufengensis (a non-hominin Miocene ape) was an extremely dimorphic species from dentition

more dimorphic than the most dimorphic living hominoid, the orangutan, and may have been more dimorphic than any living anthropoid.

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17
Q

What is important about Ms. Ples

A

nickname derived from ‘Plesianthropus transvaalensis’ - the name originally given by Broom

has small cc (485cc) but bipedal - one of first fossils to reveal bipedalism came first

Grine 2012 showed it was an adult female AFRICANUS

used by eg Dart to sex other australopithecines

young male?
(e.g., Thackeray et al., 2002)

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18
Q

What did Kimbel find regarding sediba’s relation to Homo

A

affinities with Homo in sediba MH1 skull are actually down to immaturity (eg lateral temporal lines, large post-orbital breadth, lack of flared zygomatics)

MH 1 occupies an intermediate position
between Taung and adult A. africanus crania in the depth of the infra-malar region of the face.

(Kimbel and Rak, 2017)

full-grown A. sediba holotype would have closely resembled A. africanus (as
represented by Sts 5 and Stw 505) but not early Homo

(Strauss, 2013)

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19
Q

Give examples of pathologies seen in hominin fossils

A

auditory exostoses in Neanderthal

tumour in an Australopithecus metatarsal bone

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20
Q

Give an example of a hominin that may be 1 or many species based on geography

A

Homo erectus sensu lato

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21
Q

Give an example of a hominin that may be 1 or many species based on geography

A

• Time: because of the concept of time-averaging, fossil assemblages may sample evolutionary changes within a lineage. •

The example of Australopithecus: a single lineage or two species?

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22
Q

Are south African hominins all one species?

A 
A. prometheus
3.7-2.2 Ma
A. sediba 2.0 Ma
A. africanus
2.8-2.2 Ma
•	Sterkfontein
o	Member 4 is very rich in specimens 
o	Some specimens have real range of characteristics 
o	Sex Dimorphism?
o	Ontogeny
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23
Q

What did Fornai find regarding taxic diversity in South African australopiths

A

2015: appears to be a gradient with prometheus and africanus at extremes
but difficult to interpret diversity with authority

2021:
sacrum diversity was great enough to suggest different species (Sexual dimorphism and developmental or geologic age could not adequately explain the differences between StW 431 and Sts 14)
Greater than even diversity between bonobos and chimps

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24
Q

Does boisei fossils display sexual dimorphism

A

KNM-ER 732 is smaller than 406 but similar cc
No sagittal crest in 732

consistent dimorphism between males and females with african apes but less than in gorillas or mandrills

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25
Q

What features of KNM-ER 406 are repeated in other fossils from Koobi Fora?

What does this suggest -

A

KNM-ER13750 23000 show similar medial depression in arched supraorbital torus
extremely flared zygomatics

population level variation

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26
Q

What is important about Konso boisei fossils

A

Konso is most northern location where boisei is found, also very recent 1.4mya

different to other boisei -
• Broad and short palate, unlike other boisei
• Less concave face‐zygomatic complex than other boisei
suggests variation in time or space

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27
Q

How is sexual dimorphism expressed in Paranthropus robustus?

A

Very few fossils so hard
absent sagittal crest

Size difference:
McHenry 1991
F:110 cm
M:132 cm

Grabowski et al. 2015
(based on 9 femoral fragments)
F:~ 24 kg
M:~ 32 kg

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28
Q

Summarise the morphology and diet of robustus

A

• MORPHOLOGY: adaptations to hard object (nuts, seeds) processing
• MICROWEAR: diet regularly included hard objects
• ISOTOPES: similar to Au. africanus, 30‐40 % C3‐C4 plants
• DIET: fruits, nuts; diet varied seasonally and ontogentically
• Potential role of fallback hard object foods in driving extreme
morphology probable; termites dug with bone tools?

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29
Q

Summarise the morphology and diet of boisei

A

• MORPHOLOGY: adaptations to hard object (nuts, seeds) processing
• MICROWEAR & ISOTOPES: prolonged masticatory bouts involving tough, abrasive C4 plants
• DIET: high % of C4 grasses, or sedges or their combination
• Potential role of fallback hard object foods in driving extreme
morphology unclear

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30
Q

Summarise the morphology and diet of aethiopicus

A

Paranthropus aethiopicus
• MORPHOLOGY: less efficient masticatory adaptation (very prognathic)
than boisei or robustus
• ISOTOPES: shift from mainly C3 to mainly C4 plants after 2.37 Ma

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31
Q

Give studies promoting Parathropine monophyly

A

Kimbel et al. (2004).

Gunz et al.(2012)

Turner and Wood (1993)

32
Q

What did Kimbel find regarding Paranthropine monophyly

A

Strait and Grine (2004) combined 109 non-metrical traits with 89 traits based on linear measurements and, using two differently composed in-groups, also found that the three “robust ” taxa (P. robus-tus, P. boisei
and P. aethiopicus) consistently formed a monophyletic group, result also reached by the cladistic analysis by Kimbel et al. (2004).

33
Q

What did Gunz find regarding the skull of robustus

A

Gunz et al.(2012) showed that a P. robustus
cranium, SK 48, is morelikely to be a scaled variant of P. boisei than a scaled variant of A. africanus - supports idea of a robust clade

34
Q

What did Turner and Wood suggest about Paranthropus monophyly

A

Turner and Wood (1993) assessed the probability of monophyly by examining the
biogeographic patterns of African Plio-Pleistocene large mammals. They concluded that during the time range of Paranthropus ,there was evidence in at least one mammalian group of faunal dispersal between regions, with several monophyletic groups having representatives in both regions -> lends credibility to the hypothesis of
Paranthropus monophyly

35
Q

Why is there a good case for robust similarities just being homoplasy

A

Phylogenetic studies of bovids (Gatesy et al. 1997), hippos, carnivores, Old World monkeys, elephants and equids all suggest that the evolutionary history of these groups shows evidence of substantial homoplasy during the period of time spanned by the megadont and hyper-megadont hominins.

many, but by no means all, of the characters that link
Paranthropus taxa in the same clade are related to the masticatory system. These are likely to be functionally integrated, thus potentially they are non-independent and if so, they should not be coded as individual independent characters in a cladistic analysis

the faces of Kenyanthropus platyops and Homo rudolfensis are, like P. boisei, both orthognathic relative to earlier hominins, but whereas the former have small or moderately sized postcanine teeth the latter shows extreme postcanine megadontia. Since
K. platyops and H. rudolfensis are generally not considered to be closely-related to P. boisei, the cited similarities among these taxa must be due to homoplasy

36
Q

What is a genus?

A

Generic classification in biology today, above species and below family representing:
• a group of monophyletic species
• reflect a distinct ecological niche that shapes the
evolutionary trajectory of the descendant species

37
Q

What features link aethiopicus to afarensis (2)

A

increased prognathism

a more posteriorly positioned sagittal crest that merges with the nuchal crest.

38
Q

How does africanus differ from afarensis (3)

A

africanus has higher and shorter and rounder braincase, that rarely shows sagittal cresting and that never shows compound temporo-nuchal cresting.

The nasal aperture is bordered by prominent anterior pillars and the zygomatic bone shows bossing at the transition to the temporal process.

subnasal prognathism

39
Q

How does sediba’s face differ from the other Australopiths

What are other facial features of sediba(3)

A

narrow face,

small endocranial volume,
slight facial prognathism,
no anterior pillars

40
Q

What are key features of H. habilis

A

slightly larger braincase and smaller face and teeth than
in Australopithecus or older hominins

Retains some ape-like features, including long arms and a moderately-prognathic face.
tooth enamel was still thick and their jaws strong, indicating their teeth were still adapted to chewing hard foods.

41
Q

How does rudolfensis differ from habilis (3)

Does this warrant a species difference??

Could ergaster be subsumed into either?

A

H rudolfensis (KNM-1470) vs H. habilis (KNM-ER 1813):

KNM-1813 had a small upper jaw with smaller, more modern-like teeth.
KNM-1470 had a square maxilla, while KNM-1813’s was rounded.
KNM-1470’s brow ridge was slight, while KNM-1813’s was strongly developed and pronounced.

These species do not differ from each other in the sort of ways that males and females of modern apes (including humans) differ from one another (usually related to greater musculature in males) and therefore merit a species distinction.

Homo ergaster differs from both due to its substantially larger size, brain volume, presence of nasal bones, and a less prognathic face

42
Q

How does H. erectus in Africa compare to in Asia (7)

A 
ergaster:
Thinner cranial bones, 
no sagittal keel, 
no bregmatic eminence, 
more pronounced supratoral sulcus,
More developed supraorbital torus, 
less developed occipital torus, 
slender mandibles
43
Q

Which erectus variant is most primitive

Which features are like erectus? (3)

A

georgicus (Dmanisi) - smaller cc (600cc)

Midline keeling,
Depressed parietal surfaces,
Transverse expansion of the base relative to the vault

44
Q

What are some features present in all or most hiedelbergensis specimens? (5)

A 
● low braincase profile 
● large brow ridges
● a sagittal keel
● Occipital torus.
● Robust mandible built for the attachment of strong chewing muscles
45
Q

Give key features of Neanderthal skulls that are not present in sapiens (7)

A 
low, long vault, 
occipital bun 
suprainiac fossa
Continuous and arched supraorbital torus, 
midfacial prognathism, 
a retromolar space 
a large nasal cavity
46
Q

What is the problem with the erectus holotype

A

holotype is a 500kya skull cap (Trinil 2)

a 500,000-year-old fossil specimen from Java be used as the standard point of reference for fossil specimens located on a different continent, and that are almost 4x as old?

47
Q

Where are specimens definitely habilis and where is it more controversial

A

those from Olduvai, Tanzania, including type specimen (OH7/ Johnny’s Child)

Koobi Fora is more problematic:
great morphological variation. Today, many view the Koobi Fora assemblages of fossils as representing two species; Homo rudolfensis and habilis

48
Q

What is the temporal range and distribution of rudolfensis

A

Temporal range: 2.09-1.78 Ma

Distribution: eastern Africa

49
Q

What part of the post-crania of habilis is closer to Australopithecus

A

legs were relatively short, providing this species with arm and leg proportions that were relatively ape-like and similar to those of the australopithecines

phalanges still curved (but less so) and primitive long arms and a moderately-prognathic face

50
Q

What differentiates rudolfensis from habilis

How does it compare to robusts

A

H. rudolfensis differs in its larger braincase, longer face, and larger molar and premolar teeth

teeth only slightly smaller than robusts but rudolfensis didn’t have the heavily-built jaw and strong jaw muscle attachments seen in robusts

rudolfensis has 2 rami in Broca’s cap whereas habilis has 1 (Falk, 1983)

general lack of postcranial remains: limb proportions unknown because of lack of skeletal material
assumed to be bipedal but without the ability to move in a fully human locomotion

51
Q

What is generally agreed about who lived in the Turkana Basin 2-1.5mya

A

Homo rudolfensis,
Homo habilis,
Homo ergaster,
Paranthropus boisei.

52
Q

How did habilis require the adjustment of Homo requirements

A

reducing lower limit of brain size

53
Q

What suggests habilis should be moved to Australopithecus

A

Naming this species required a redefining of the genus Homo (e.g., reducing the lower limit of brain size)

lacks the ability to ER like erectus

ape-like limb proportions and curved phalanges

habilis shows primitive Broca’s cap (1 branch) although Tobias (1987) disputes this saying
“The two major cerebral areas governing spoken language in modern man are well represented in the endocasts of H. habilis”

54
Q

Describe the Retention of primitive characters not seen in later hominins seen in H. georgicus

A

○ Absence of humeral torsion
○ Small body size
○ Low encephalization quotient (EQ) and small cc (600cc)

55
Q

Give the similarities of georgicus to habilis and erectus

A 
Similar to erectus:
● Midline keeling
● Depressed parietal surfaces
● Transverse expansion of the base relative to the vault
● Erectus like inner-ear
Similar to habilis:
● The skull is small and rounded at the back
● In profile the face resembles 1813
● no occipital torus is present
● Shallow palate
● Small brain
56
Q

How does Turkana Boy (KNM-WT 15000) compare to Lucy in

a) vertebrae
b) limbs

What are the functional implications

A

a) Vertebrae: speech requires a complex coordination of breathing muscles to vary pitch and produce long sentences.
Lucy and Turkana boy’s relatively narrow spinal cord compared to modern humans indicates that they lacked the nerves responsible for this fine control of the muscles that coordinate breathing during speech.

b. Limbs: Turkana boy has longer arms than legs, unlike Lucy. This highlights a reduced need for long arms for climbing trees. Longer legs increase the energetic efficiency of walking

57
Q

How does Turkana Boy (KNM-WT 15000) compare to Lucy in

a) pelvis
b) thorax

What are the functional implications

A

a. Pelvis: the Homo ergaster pelvis is narrow and human-like. Lucy’s pelvis is wider, potentially to help climb trees
b. Thorax: Homo ergaster has a barrel shaped rib cage, whereas Lucy’s ribcage is conical. The conical ribcage enables greater movement of the shoulder, and more room for a large gut to digest a plant-based diet. Homo ergaster likely has a smaller gut and a diet that included food which required less time to break down.

58
Q

What is key to note about the Trinil 1 femur

Why is it different to Turkana boy’s femur

What explains this

A

Trinil Femur I shows none of the characteristics typical of early Homo femora (relatively long neck and a small femoral head, and a shaft that is wider from side-to-side than front-to-back)

can be attributed to broader changes in pelvic morphology occurring within the Homo lineage between the Early and late Middle Pleistocene. These changes are thought to be associated with the evolution of rotational birth

Trinil Femur 1 is a relatively modern human femur that ended up buried close to the Homo erectus fossils due to the complex stratigraphic processes of the site.

59
Q

How did the Homo pelvis change from the Early to late Middle Pleistocene?

What fossils is this seen in?

What did this allow and what is the importance?

A

pelvic outlet expands antero-posteriorly, front-to back, allowing the pelvis to become less wide mediolaterally.

difference between Trinil 1 femur and Turkana Boy femur

Rotational birth allowed the pelvis to become narrower and the femoral neck to become shorter, both of these reduce mediolateral bending stress of the femur in later Homo and reduce the energetic costs of locomotion by reducing the muscular costs of keeping the body erect during the single leg phase of walking.

60
Q

Give a primitive and derived trait in naledi’s femur

A

Long neck relative to head diameter, associated with wide hips and non-rotational birth (primitive)

derived: Prominent linea aspera

61
Q

Give 4 erectus-like and 3 Neanderthal/human-like traits in heidelbergensis

A 
erectus like:
● low braincase profile 
● large brow ridges
● a sagittal keel
● Occipital torus.

later Homo-like:
● Little postorbital constriction
● teeth were smaller than those of earlier species but were larger than those of modern
humans
● Some members of this species possessed a gap, called the retromolar space, behind
the third molars at the back of the jaw. Others had only a tiny gap or no gap.

62
Q

What are some key differences between the available post-cranial elements of “Ardi” and
“Lucy”?

A

Pelvis of lucy is more human-like

The upper portion of each hip bone, the ilium, is short and curved compared to the long, flattened ilium of chimpanzees and other apes. The curvature places the attachment of the quadriceps muscle closer to the front of the body, allowing the muscle greater leverage in pulling the femur forward in an upright posture

63
Q

What were the key changes in the hominin lineage during the muddle in the middle

A

greater encephalization and smaller teeth, and likely the differentiation of geographic groups.

64
Q

What is a key problem with the heidelbergensis holotype`

A

used the Mauer mandible

mandibles are extremely plastic and may or may not reflect associated morphological changes in the crania

heidelbergensis cranium then had to be reconstructed indirectly

65
Q

How can heidelbergensis be related to Neanderthals

A

represents either (and sometimes paradoxically both) the generalized Middle Pleistocene hominin, or a chronospecies of Neanderthals

66
Q

When was the Linnaean taxonomy developed

A

prior to the development of evolutionary theory.

67
Q

According to Roksandic what species do SH hominins represent

Why

A

early members of the Neanderthal lineage (430kya)

already show hyper-derived dentition,as well as a number of Neanderthal derived traits in cranial and mandibular morphology

(Roksandic, 2021)

68
Q

What is a problem with giving Chinese specimens heidelbergensis

A

comparisons of maximum and minimum frontal breadths on a range of fossils from Europe, Africa, and China showed that hominins like Petralona, Bodo, and Kabwe cluster relatively close together and well away from the Chinese fossils

(Roksandic, 2021)

69
Q

What is a problem with considering heidelbergensis as the LCA of sapiens and Neanderthals

A

since the MRCA of the modern human and Neanderthal lineages has been pushed further back in time toward the late Early Pleistocene or very early Middle Pleistocene,8the specimens currently assigned to H. heidelbergensis sensu lato cannot be considered representatives of the MRCA

(Roksandic, 2021)

70
Q

Give 2 reasons H rhodesiensis should be suppressed

A

1) the taxon is poorly defined and variably understood and used;
(2) the taxon name is associated with sociopolitical baggage that our scientific community is trying to dissociate itself from

(Roksandic, 2021)

71
Q

Give key features of H. bodoensis

A

arched SO tori separated by glabella
sagittal keeling
long low skull with flattened frontal
increased cc and associated traits (eg reduced PO constriction)

(Roksandic, 2021)

72
Q

a) How does H bodoensis differ from erectus

b) How is it similar to erectus

A

a) increased cranial capacity (intermediate between H. erectus and sapiens) and a suite of associated derived traits

b) robustly built midface;
total facial prognathism; projecting tori and a flattened low frontal squama;
sagittal keeling;
low vault profile

(Roksandic, 2021)

73
Q

What is the endocranial capacity of Bodo 1

What is another interesting feature of this specimen

A

~1250cc

series of cutmarks on skull interpreted as intentional postmortem defleshing.

(Roksandic, 2021)

74
Q

What is a key derived feature of bodoensis

How does it differ from Neanderthal

A

increased cc
his trait is presumably already under selection in the MRCA in the latter portion of the Early Pleistocene

does not show any of the Neanderthal-specific morphology associated with midfacial prognathism and neurocranial shape
Neanderthals have continuous SO tori

(Roksandic, 2021)

75
Q

What was the distribution of bodoensis

A

pan-African distribution with the peripheral range extending into the eastern Mediterranean (Southeast Europe and the Levant) from which it could have contributed to there population of European (and possibly Central and East Asian) demo-graphic sinks after the glaciation

(Roksandic, 2021)

76
Q

Where does bodoensis fit with the hominin family tree

A

H. bodoensis separated from the Eurasian groups before the split of the Eurasian forms into Neanderthals, Denisovans, and possibly other groups.

While essentially an African species, H. bodoensis may have played a role in the evolutionary history of the Levant and Europe

(Roksandic, 2021)

Human Evolution (16 decks)

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