The arboreal origins of human bipedalism
Summary (3 min read)
A. Board Composition and the Firm’s External Environment
- An operating assumption of much of the corporate governance literature is that boards are endogenously determined institutions.
- On the basis of this premise, much of this literature focuses on the proportion of outside directors and the link between performance and corporate governance.
- It is possible that political directors are neither more effective monitors than other types of directors nor involved in rent-seeking activities but are on the boards of regulated industries because there is less market pressure to appoint more effective monitors and greater opportunities for shirking by the CEOs of regulated companies.
- In effect, regulated firms need or simply have less effective monitoring by their boards than firms that are not regulated.
B. From Market to Political Competition: A Primer on Natural Gas Regulation
- The business environment of natural gas companies has changed dramatically over the history of the industry.
- 20 This section draws heavily on the discussion of the natural gas industry found in Robert L. Bradley, Oil, Gas, and Government: The U.S. Experience (1996); Stephen Breyer, Regulation and Its Reform (1982); and M. Elizabeth Sanders, The Regulation of Natural Gas: Policy and Politics 1938–78 (1981).
- At several points during the late 1940s, the FPC commissioners tried to expand their regulatory authority to include producer prices.
- Producer states in the late 1940s grew concerned, and on two occasions tried to enact legislation that would clarify that the FPC did not have the authority to regulate the prices charged by independent producers.
- Finally, all extraction was deregulated in 1986 by Federal Energy Regulatory Commission (FERC) Order 451, which set the regulated price above the marketclearing price.
C. Defining Regulation
- Given the different types and durations of regulatory regimes in the natural gas industry, the authors must be careful to clearly identify the particular regulatory events on which they focus.
- Thus, for the Moody’s sample, the authors define a firm as regulated in a given year if (1) it lists one of its lines of business as owning a pipeline in any year after 1938 and/ or (2) it lists production as a line of business in the 1955–80 period.
- Note that this definition biases their results toward zero; pipeline ownership does not necessarily mean the firm is regulated, since the pipeline may not cross state boundaries.
- Clearly, the 1978 act deregulated some portion of production.
- The oil industry was also subject to regulatory expansion during their sample period.
III. Director Classification and Trends
- To create their sample of corporate boards the authors identify all the natural gas companies listed in Moody’s Industrial Manual.
- As shown in Table 2, between the two sources the authors are able to construct a sample that includes biographical data on more than 60 percent of the directors in any given observation year.
- Finding a growing diversity of backgrounds among board members (that is, more of other nonpolitical director types) caused by regulation might suggest that the demand for regulators is not unique to their regulatory background.
- The corporate finance literature typically classifies directors as insiders, outsiders, or “gray.”.
- One problem with the Moody’s-Marquis data is that the authors are limited to those directors they can identify in Marquis.
B. The Proxy Statement Sample
- Given the limitations of the Moody’s-Marquis data, the authors supplement their analysis with an additional sample that consists of 96 natural gas firms.
- Table 3 gives the breakdown by firm-year and total number of directors.
- The authors fall short of this total because (1) several firms have missing proxy statements for several years, making it impossible to construct the board, and (2) the majority of firms operated only for a subset of the sample period.
- The proxy data set has several advantages over the Moody’s-Marquis sample and one major disadvantage.
- The major disadvantage is that the data extend back only to 1977.
C. Preliminary Data Analysis
- Figure 1 presents the proportion of directors that are Washington lawyers by year and industry segment.
- 38 Although proxy statements exist prior to 1978, their efforts to obtain them from the SEC met with limited success.
- For pipeline companies, the number of Washington lawyers rises dramatically in 1940 and remains around 8 percent throughout the remainder of the sample period.
- Given that production companies are deregulated beginning in 1978, this rise and fall is consistent with the external environment hypothesis that regulation requires firms to focus attention on the political process.
- The trends for regulators and the composite indices are similar.
A. Control Variables for the Moody’s Data Set
- Moody’s provides firm-specific data that the authors use as controls given previous findings in the literature.
- The authors also include the size of the board, as the opportunity cost of a given director type is likely to change as the board size grows.
- These variables control for the general economic environment common to all firms in a specific segment of the industry.
- The authors have far better performance measures for their proxy statement sample.
- As noted above, for holding companies or firms with pipeline operations, the authors code the regulation variable as one after 1938.
B. Control Variables for the Proxy Data Set
- The independent variables for the proxy data set come from both the firms’ proxy statements and COMPUSTAT.
- In general, the authors follow the existing literature on board composition in choosing their controls.
- Finally, the authors include the firm’s debt-to-asset ratio to account for external financial pressures and sales as a proxy for firm size.
- As before, the firm’s regulation variable is coded one if any of its lines of business is regulated in the observation year.
- The lower section of Table 4 contains summary statistics of the sample.
C. Estimation Procedure
- Because the dependant variable is a count of the number of directors of each type on the board, ordinary least squares will be biased and inconsistent.
- Following Benjamin Hermalin and Michael Weisbach,42 the authors estimate a Poisson model.
- 41 The proxy statements and COMPUSTAT SIC codes do not identify companies that hold leases for other production companies or holding companies independently from the other categories.
D. Results from the Moody’s Data
- The cross-sectional results of the regulation effect for the Moody’s-Marquis sample are presented in the top section of Table 5.
- Former regulators are also more common on the boards of regulated companies.
- Only composite 3 (former regulators and politicians) is not statistically significant.
- The last rows of Table 5 present results of the new-director model using firm-specific fixed effects.
E. Proxy Statement Sample
- Table 7 presents results of the models using the proxy statement data for the period 1978–98.
- In addition, composites 1 and 4 are statistically significant, which indicates between .259 and .752 additional political directors depending on the measure.
- Nevertheless, the authors find that Washington lawyers are more common on boards of regulated companies.
- Finally, the last rows present results for the model examining only newly appointed directors.
- In general, the results indicate little difference between the boards of regulated companies and unregulated companies in the numbers of other director types.
V. Conclusions
- The authors examine the role of political directors on the boards of regulated companies.
- The first explanation is that these directors play an advisory role, providing information, expertise, and/or political access to resources relative to the firm’s external environment.
- The authors examine the regulation of natural gas pipelines in 1938 and natural gas producers in 1954 and the 1986 deregulation of natural gas wellhead prices.
- The authors do find evidence of broader changes in the composition of corporate boards in the 1930–90 sample period.
- The authors examine the possibility that regulated firms are simply less effectively monitored and hence have more directors with political backgrounds simply because they are less effective monitors than other types of directors.
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Citations
31 citations
Cites background from "The arboreal origins of human biped..."
...…al. 2001; Haile-Selassie 2001; White et al. 2009; Brunet et al. 2002; Schmid 1983; Stern 2000, Alemseged et al. 2006; Green and Alemseged 2012; Nakatsukasa 2004; Galik et al. 2004; Pickford 2006; Pickford et al. 2002; Crompton et al. 2008; Senut 2012a, 2012b, 2014, 2016; Thorpe et al. 2007, 2014)....
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...The structure of the woodland environment is important in relation to the weight of the animal and the flexibility of the substrates (Thorpe et al. 2007, 2014)....
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...…knuckle- walkerlike chimpanzee or a vertical climber (Keith 1923; Gregory 1930; Morton 1935; Washburn 1967; Tuttle 1969, 1977, 1981; Stern 1975, Prost 1980; Fleagle et al. 1981; Coppens & Senut 1991 for comprehensive articles; Richmond et al. 2001; Thorpe et al. 2014 for an historical perspective)....
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18 citations
Cites background from "The arboreal origins of human biped..."
...335 This speaks to recent debates about the origins of hominin bipedalism and the importance of complex 336 topography (Winder et al., 2013, 2014) which challenges the more conventional arboreal hypotheses 337 (Thorpe et al., 2007, 2014a, b; Crompton et al., 2010)....
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13 citations
11 citations
10 citations
Cites methods from "The arboreal origins of human biped..."
...This suggestion, based on carpal morphology, has been widely adopted in the human evolution literature (e.g. Le Maître et al., 2017; Macho et al., 2010; Saunders et al., 2016; Schilling et al., 2014; Simpson et al., 2018; Thorpe et al., 2014)....
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...This hypothetical postural difference has since been relatively well adopted within the literature, and has subsequently been upheld as kinematic evidence of fundamentally different forms of knucklewalking (Le Maître et al., 2017; Macho et al., 2010; Saunders et al., 2016; Schilling et al., 2014; Simpson et al., 2018; Thorpe et al., 2014)....
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References
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"The arboreal origins of human biped..." refers background in this paper
...Hunt and colleagues (1996) advocated much-needed uniformity in the language used to describe locomotion across primate clades....
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...Hunt 1992; Remis 1995; Thorpe & Crompton 2005, 2006). It was from this that Hunt (1996) and Stanford (2006) developed the arboreal foraging hypothesis....
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...The approach revealed that all great apes occasionally choose to engage in arboreal bipedalism—walking along and between branches on two legs (e.g. Hunt 1992; Remis 1995; Thorpe & Crompton 2005, 2006)....
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Frequently Asked Questions (11)
Q2. What is the important line of evidence to emerge relatively recently from new fossil discoveries?
Published online by Cambridge University PressD ebat eone of the most important lines of evidence to emerge relatively recently from new fossil discoveries is that adaptations to suspension and arm-swinging must have evolved not once only but convergently, across several millions of years, in multiple fossil ape species (e.g. Almecija et al. 2009).
Q3. What is the origin of hominin bipedalism?
Theories regarding the origins of hominin bipedalism have spent some considerable time ‘on the ground’ as a result of the knuckle-walking hypothesis, which postulates that their earliest bipedal ancestor evolved from an ape that knuckle-walked on the ground in a way similar to modern chimpanzees or gorillas.
Q4. What is the evolution of the hominoid ancestor?
Locomotion and posture from the common hominoid ancestor to fully modern hominins, with special reference to the last common panin/hominin ancestor.
Q5. What is the effect of bipedalism on the orangutan?
The authors also found that in 75 per cent of their observations of orangutan bipedal locomotion along branches, they used their hands for stabilisation, as do chimpanzees (Hunt 1996; Stanford 2006).
Q6. What was the significance of the approach?
The significance of the approach was that it allowed comparative quantification of the ecological context of locomotion (how much time a particular species spent in knuckle-walking, brachiating, vertical climbing, etc.; in what kinds of setting— e.g. forest canopy, forest floor, open grassland—and an indication of the stresses different behaviours placed on the body).
Q7. How did the footprints from Laetoli show that hominin ancestors?
The famous footprints from Laetoli in Tanzania show that hominin ancestors were walking upright by at least 3.65 million years ago.
Q8. What is the main argument for bipedalism?
Despite the longevity of the paradigm that derived human bipedalism from chimpanzeelike knuckle-walking, the authors conclude that the arboreal origin of bipedalism is now overwhelmingly supported by the fossil, biomechanical and ecological evidence.
Q9. What is the important line of evidence for the evolution of the ape?
By the early 2000s the fossil record of the Eurasian and East African Miocene (23–5 million years ago (Ma)) was burgeoning and revealing the body form of early ‘crown’ hominoids (‘crown’ hominoids being the direct ancestors of all living apes, including humans).
Q10. What is the main challenge to Winder et al. 2013?
Explaining how their ancestors survived a locomotor transition in a relatively dangerous semi-open habitat remains a critical challenge to these hypotheses” (Winder et al. 2013: 334).
Q11. What evidence did Tuttle have for upright apes?
Thus features such as their broad, shallow trunks; scapulae positioned on the back rather than side of their bodies, and lumbar vertebral bodies that increased in size towards the lower end of the spine all indicated that these species were frequently upright (MacLatchy 2004; Moyà-Solà et al.