The evolution of bipedalism

[Gerrard Farrell]

I wrote the following material elsewhere on the Biomch-l site but feel it has a place in this thread. The development of bipedalism was likely caused by multiple drivers but the key element was the development of ground up kinetics energy from the legs into hand held objects particularly hunting implements like rabbit sticks.

Update

• May 7, 2019, 03:53 AM
  Re: Quadruped to biped . Not possible in terrestrial apes .
  
  So the title of this thread was "Quadruped to biped . Not possible in terrestrial apes " . But , on further reflexion ,perhaps it is . If you take fighting out of the equation , introduce sex for all and isolate your population from more agressive qaudrupeds , change towards a biped might be possible . A case in point would be the Bonobo . Interesting !
  Last edited by Gerrard Farrell; May 7, 2019, 07:54 AM.

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  Gerrard Farrell
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  #5
  July 7, 2019, 08:27 AM
  Re: Quadruped to biped . Not possible in terrestrial apes .
  
  About 1.5 million years ago a last common ancestor gave rise to the ancestors of the modern day Bonobo (Pan Paniscus ) and Chimpanzee (Pan Troglodytes ) .
  
  Bonobos are found south of the river Congo and Chimps to the north ,and some have speculated that it is the geographic separation of the two species by the Congo and one of its tributaries , that has allowed the Bonobo to evolve differently than the Chimpanzee .
  
  But ,given time ,could you get from a Bonobo to a biped and would that process be similar to that which occurred 7 million years ago when a last common ancestor gave rise to Pan and Homo .
  
  One mechanism by which a Bonobo might give rise to a habitual biped is as follows .
  
  It is known that Bonobo society is dominated by females and that males displaying violent behavior towards females is prevented by female coalitions . Some have also forwarded the idea that alpha males in a group are selected not by males fighting each other for dominance but by female selection . It would appear therefore , that for a male to get ahead in Bonobo society ,they must have the goodwill of high ranking females . But if you are not the son of a high ranking female how do you ingratiate yourself with the decision makers ?
  
  Well , favorable personality traits such as empathic behavior might boost your standing a bit , but the ability and willingness to provide females with a regular supply of meat is really going to make you popular . But how ?
  
  Well let's say that through prolonged brachiation and perhaps a genetic mutation or two we get a Bonobo with long limbs , plenty of energy storing ligament and a pelvis that can be set at 60 or seventy degrees to the plane of the shoulders . ( Such an animal would be not unlike extant Gibbons in its ability to walk upright )
  
  Now let's say our "tending towards upright" , hungry , Bonobo is confronted by a tree full of feeding/roosting birds . Every time it attempts to ventured near the base of the tree , the birds fly away . In frustration the Bonobo picks up an old broken femur bone which happens to be lying nearby and ,with the ability to stand upright and separate the plane of its shoulders from the plane of its pelvis ,and using both hands , it flings the bone ,at speed , up into the tree . And out falls a bird with a broken wing . Bingo
  Last edited by Gerrard Farrell; July 7, 2019, 12:45 PM.

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  Gerrard Farrell
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  #6
  July 8, 2019, 02:02 PM
  Re: Quadruped to biped . Not possible in terrestrial apes .
  
  Let's say our Bonobo ,equipt with his newly discovered bird gathering ability ,becomes a big hit with the ladies and has many offspring . Might those offspring and their descendants become progressively better adapted to a two handed throw ( like swinging a baseball bat but letting go at the appropriate moment ) ,both physically and neurologically .
  
  From the neurological perspective might subsequent generations ,given the nature of a full body throw aimed in a particular direction , develop genetically dictated left or right side dominance , not just for fine motor tasks but for also for more general tasks .
  
  In effect , might we get the development of population handedness , were right/left side dominance affects not just the hand of choice for a task but also ,for example ,is linked to a dominant eye ?
  Last edited by Gerrard Farrell; July 9, 2019, 06:43 AM.

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  Gerrard Farrell
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  #7
  August 1, 2019, 05:34 AM
  Re: Quadruped to biped . Not possible in terrestrial apes .
  
  From post Uncategorized Groups - " In frustration the Bonobo picks up an old broken femur bone which happens to be lying nearby "
  
  Why an old femur bone and not a simple stick ? Well it has to do with physics and the effectiveness of a thrown hunting tool .
  
  If you try and throw a stone using a two handed grip , it will leave your hands at the same speed as your hands were travelling at the moment of release . Let's say 10m/s .
  An animal 20m away has 2 secs to get out of the way and only requires to move a short distance to do so . However ,if you throw a stick , the center of mass will be some distance from your hands at release and so moving faster (through a wider arc) . The thrown stick will therefore move towards the prey animal faster than the stone would , giving it less time to react . In addition the stick would be rotating about an offset center of mass giving a wider " hit area " and so a better chance of hitting the prey animal .
  
  With a broken femur held at the broken end , the center of mass would be located close to the thickened , let's say distal , part of the bone . So even greater speed at release and an even wider " hit zone " as the bone rotates about the center of mass .
  
  To recap then , perhaps 7 million years ago a Bonobo like animal evolved . Through brachiation and a female dominated society with less aggression , a trend towards longer limbs and a rotating trunk developed . Through trial and error , the Bonobo like animals found sticks ,naturally weighted at one end ,could be used for knocking birds out of trees .
  
  Time passes ,the animals develop bodies better adapted to two handed throwing , and the size of prey animals increases .
  
  It's not long before you get prey such as small ,thin legged antelope being driven by some hunters into the stick throwing range of hidden others , where such antelope are disabled and ultimately killed .
  
  Looking back through this thread the most unlikely part of the story is the evolution of a female dominated ,bonobo like society ,from a chimp like last common ancestor . And yet it has happened in the Congo area .
  
  Any thoughts ?

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  Edmund Cramp
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  #8
  August 2, 2019, 02:07 PM
  Re: Quadruped to biped . Not possible in terrestrial apes .
  
  I do find this conversation interesting, it makes me think and that's always entertaining - I thank you for this. But if evolution was influenced in the way discussed, why are there so few examples of bipedal animals? This is not an area that I would claim any serious knowledge of but when you look at the whole animal kingdom it seems to me that you could equally make the argument that bipedalism is an evolutionary dead-end as the vast majority of life is not bipedal and catches its next meal with limbs and teeth, not by throwing things. If the ability to throw solid objects was a benefit to survival then why is it so rare in the animal kingdom? On the other hand, the argument could be that bipedalism is so effective that we attack and eradicate any animal that attempted to invade our evolutionary space, but that would be a dead-end...
  
  My feeling is that bipedalism has freed up the development of the hands, not to throw anything or hunt but to enable us to create and use tools and be more social and caring of other members of our species.
  
  Edmund Cramp

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  Gerrard Farrell
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  #9
  August 4, 2019, 04:09 AM
  Re: Quadruped to biped . Not possible in terrestrial apes .
  
  Hi Edmund ,
  
  Thanks for replying to the thread .
  Quote
  
  "My feeling is that bipedalism has freed up the development of the hands, not to throw anything or hunt but to enable us to create and use tools and be more social and caring of other members of our species."
  
  No matter what twists and turns were involved in the eventual evolution of Homo Sapiens , my main interest in the subject is how bipedalism was select for in a group of knuckle walkers , which is what many believe our last common ancestor with the Genus Pan ,was .
  
  It is not uncommon in nature to find animal species have a single trick or adaptation that other don't , and which has allowed them to flourish . For example the archer fish or the electric eel . I think it is quite plausible that the ability to throw sticks at high speed ( and speed is key here ) might have evolved in a "Bonobo like setting " and so added to a brachiation induced , and already existing , trend towards longer limbs and bipedalism .
  
  Is there any evidence that the ability to throw sticks at high speed make a big difference to the viability of a hominin species ? Well it's simple enough to be within the compass of our distant ancestors but successful enough to still be in use today . For example , rabbit sticks were still used by humans , for life or death hunting purposes , until very recently (Native American Indians ,Aborigines) and might even have been the first valued possession among the earliest hominids .
  
  Why are there not more stick throwing Hominin species around ? Neanderthals were around until about 40,00 years ago .It would appear our ancestors bred with some of them ( 2% of a modern Western Europeans DNA is Neanderthal in origin ) and out competed or killed off the rest . Sadly humans are quite capable of killing off a competing species . Capable even of genocide .
  
  Are humans an evolutionary dead end . Until recently I thought we probably were but after reading a bit about the Bonobo perhaps there might be some hope . As women become more influential in the world , something that men instinctively resist , we might become more viable long term .
  
  Sorry lads !

[Edmund Cramp]

Re: The evolution of bipedalism

That's a fascinating video Gerrard - maybe it's just me, but do you get the impression that the animals are aware of the audience and seem to be playing for them? I wonder if someone could take the video and place a tall black monolith in the background ...

[Gerrard Farrell]

Re: The evolution of bipedalism

Hi Adam ,
Some believe that the last common ancestor of Homo and Pan was an animal close to our modern day chimp and the type of tools I envisage being used by the first of our obligate bipedal ancestors would be similar to those used by modern day chimps or monkeys . Such tools would include large sicks , rock and anvil assemblages (Capuchin monkeys ) or simple ,hand held throwing items . The main point to remember is that an early biped could likely develop more power in the tools making them more effective . It's not so much that a chimpanzee like animal can't figure out that a long stick could be a good weapon ,it's just that they lack the phenotype to make using such a weapon worthwhile . (see 2 min video below it shows two chimps in conflict . One tries to use a long stick as a weapon on it's opponent but soon drops the stick when this approach fails . The first 50 secs of the video can be skipped )

The modern gibbon probably lacks the marbles to swing or throw a stick to great effect but if you combine a chimp brain with a gibbon like phenotype you are in business with a high speed tool user . This , I believe , is probably why our earliest bipedal ancestors remained bipedal when they gave up a brachiating lifestyle .


So here is that video . The stick wielding chimp seems to try out the stick as a weapon with a few practice swing before going after its troop mate . This fails .
Now imagine the damage a five year old child could cause swinging a golf club at a car door . Our early ancestors would not have golf clubs but may well have had a access to heavy woods such as ironwood . So for early bipeds its not about more sophisticated tools but about the more sophisticated use of tools which is allowed by a bipedal phenotype .

Crazy Chimps Fighting at the LA Zoo (with a big stick)! - YouTube

▶ 1:56

https://www.youtube.com/watch?v=6lQcKiFy_DM



3 Jan 2012 - Uploaded by dancheng2
Crazy chimps beat each other, chase one into a ravine, and in the finale, a chimpuses a big stick to beat ...

[Adam Clansey]

Re: The evolution of bipedalism

Alright Gerry,

I thought I’d rekindle this fascinating discussion and thread.

Going back to some of your previous posts on the theories put forward for natural selection choosing bipedalism as an advantageous adaptation to move, I am slightly confused what you mean by the term ‘tool use,’ can you elaborate on this? The reason for asking is that phrase ‘tool use’ implies to me anyway, that the genus homo had the cognitive capacity or smarts to be able to build, develop and use tools for effective survival?

My knowledge in the area of evolutionary biology is limited but given that evolutionary scientists/theorists unfortunately only have bone fossils records to go by, I’ve always wondered how the neural circuitry and CNS adapted to the structural/functional morphology adaptations from quadrupedalism to bipedalism and what drove what?

Speaking of smarts, I don’t know whether you watched the recent documentary called Blue Planet II on BBC (narrated by David Attenborough) but there was a scene in episode 5 called green seas that blew me away. During this episode the film crew captured footage for the very first time of an Octopus behaving in unique manner. A small shark like creature was attacking the Octopus, and during the attack the Octopus managed to use its tentacles by sticking them in the gills of the shark thus preventing the shark from breathing so it could be released. Then after that encounter the Octopus gathered lots of rocks and shells with its tentacles. Using these objects as tools, the Octopus disguised itself as a rock type structure in order to confuse the predator. In the end the Octopus lived to tell the tale. The wonders of nature hey!

And slightly off topic, I suppose what’s even more fascinating is what evolutionary chance event caused hominids to have the unique ability to contemplate the origins of life or in this case bipedalism? ;-)

Adam

[Gerrard Farrell]

Re: The evolution of bipedalism

Here are some further posts made originally be me ,today, on "Podiatry Arena "

Posts

• With regard to the above it would appear that babies can hold their bodies in an upright position long before they can balance on their feet . Included below is a link to a video of a man balancing babies on the palm of his hand with the babies holding themselves straight whilst the man moves his hand to keep them balanced . A bit like the head of the tibia balancing on the taloncalcaneal complex with the intrinsics keeping things in balance .
  
  Note -in the video the authors point out that the activities shown in the video should not be tried at home !
  
  Video
  Icelandic swim instructor teaches babies to stand on their own ...
  
  ▶ 1:45
  
  20 Jul 2017 - Uploaded by Business Insider UK
  Snorri Magnusson is Iceland's "Baby Whisperer." The swimming instructor teaches babies as young ...
  
  Gerrard Farrell
  
  Glasgow
  scotfoot, Today at 11:11 AM
  #8
• 
  scotfootActive Member
  
  
  Look at figure 6 in the paper below . Again, Luke Kelly .
  
  Intrinsic foot muscles have the capacity to control deformation of the ...
  
  rsif.royalsocietypublishing.org/content/11/93/20131188
  by LA Kelly - 2014 - Cited by 50 - Related articles
  29 Jan 2014 - We test the hypotheses that activation of the three largest plantar intrinsic foot muscles, abductor hallucis, flexor digitorum and quadratus plantae is associated with muscle stretch in response to external load on the foot and that activation of these muscles (via electrical stimulation) will generate sufficient ...
  
  Gerrard Farrell
  
  Glasgow
  scotfoot, Today at 11:55 AM
  #9
• 
  scotfootActive Member
  
  
  Further to the above , an extremely interesting paper was very recently published , Koyama et al 2017 (below) , which looked at fatiguing the muscles of the foot and the effect this has on postural sway . They found that the exercises reduced some aspects of postural sway .
  The authors stated -
  
  "This study revealed that fatiguing foot muscle exercises decreased foot muscle strength and altered postural sway during standing. Interestingly, the fatiguing foot muscle exercises decreased the COP range and velocity while standing compared with the pre-fatigue conditions. The decreased foot muscle strength after the exercises was not associated with changed postural sway during standing after the exercises ".
  
  What makes this paper so interesting is that the exercises used in the study would have fatigued the extrinsic foot muscles but not the intrinsics ( calf raises and toe curls do not target the intrinsics and a toe grip dynamometer measures extrinsic toe flexor strength )
  
  Contrary to the interpretation of the authors I believe this paper may show better postural stability with less extrinsic foot muscle input and greater reliance on the intrinsics .
  
  Paper
  Altered postural sway following fatiguing foot muscle exercises - PLOS
  
  journals.plos.org/plosone/article?id=10.1371/journal.pone.0189184
  by K Koyama - 2017
  7 Dec 2017 - The activities of the intrinsic and extrinsic plantar muscles contribute to postural stability during upright standing, especially in the single-leg standing [9]. Foot muscle strength is considered to be one of the important essentials that provides postural control while standing [10]; however, the relationship between foot muscle ...
  
  Gerrard Farrell
  
  Glasgow

[Gerrard Farrell]

Re: The evolution of bipedalism

Recently ,in the process of comparing the Chimpanzee rearfoot to that of a human it occurred to me that of one of the ways in which the intrinsic foot muscles contribute to balance might be as follows
.
The question I asked myself was what type of balance system can take the apparently difficult to balance , tall ,top heavy ,human phenotype and use this shape to advantage ?

Well , first consider balancing a pencil on your finger . Its very difficult .
Easier to balance is a long broom handle due to inertia . Easier still is the act of balancing a complete broom on your finger /palm with the broom head in the air and the end of the broom on your hand .
So can the head of the tibia balance in this way on the talus/calcaneal unit ? I think the answer may be yes , at least for postural stability in the medio lateral direction .

Previously , Luke Kelly (1) has shown that the intrinsic foot muscles can control foot posture including the condition of the medial longitudinal arch and ,in my opinion ,this could lead to inversion and eversion of the calcaneus, and then via the talus ,to a movement of the tibal head relative to the COG .

Another paper has shown that the vestibular apparatus has a direct link to some of the intrinsic foot muscles showing the have a key role in balance . (2)

A third paper (3) indicates that in the absence of strong intrinsics the extrinsics seem take on more of role in postural stability an so enlarge .

So what I am saying overall is that the intrinsics handle small medio lateral perturbations via calcaneal positioning and with larger perturbations the extrinsics kick in to assist .

This theory places the intrinsics right at the very heart of human balance .

Any thoughts





Paper 1 Recruitment of the plantar intrinsic foot muscles with increasing ...

https://www.researchgate.net/.../515...nsic_foot...22 Dec 2017 - Full-text (PDF) | The aim of this study was to determine the difference in activation patterns of the plantar intrinsic foot muscles during two quiet standing tasks with increasing postural difficulty. We hypothesised that activation of these muscles would increase with increasing postural demand...






Paper 2
vestibular modulation of the abductor hallucis and the ... - Scholars' Bank

https://scholarsbank.uoregon.edu/xmlui/bitstream/.../Final Thesis-Wallace.pdf?...1
by J Wallace - 2016 - Related articles
explore the vestibular system. The purpose of this experiment was to determine if intrinsic foot muscles are modulated by vestibular activity and to elucidate any changes in the association between the vestibular stimulation and electromyography (EMG) responses in response to changes in head position, visual cues, and ...

Paper 3
Foot muscle morphology is related to center of pressure sway and ...

https://www.ncbi.nlm.nih.gov/pubmed/28575753

by X Zhang - 2017 - Related articles
Gait Posture. 2017 Sep;57:52-56. doi: 10.1016/j.gaitpost.2017.05.027. Epub 2017 May 25. Foot muscle morphology is related to center of pressure sway and control mechanisms during single-leg standing. Zhang X(1), Schütte KH(2), Vanwanseele B(3). Author information: (1)Human Movement Biomechanics Research ...

Gerrard Farrell

Glasgow

[Edmund Cramp]

Re: The evolution of bipedalism

Thank you for the suggestion, I'll add that to my reading list. I do find these discussions very educational, they promote a host of new ideas and thoughts - if only I had more time to follow them all up. As a child back in the 1950's I was fascinated by the discussions that seemed to imply that our earliest ancestors might go back half a million years, and now this time frame keeps being pushed further and further back. Every time we learn a little more about human evolution, we discover that there is so much more than we suspected in our past. It really is A Wonderful Life!

[Michael Rainbow]

Re: The evolution of bipedalism

I really enjoyed reading this thread! Lots to think about now. FYI. There is a great chapter (15) by John Fleagle and Dan Lieberman in the book 'Great Transformations in Vertebrate Evolution' edited by Dial, Shubin, and Brainerd (2015) that nicely summarizes some of these topics. Eddie, Wonderful Life by Gould also had a tremendous impact on me. There is a new book out by Jonathan Losos called 'Improbable Destinies' (2017) that uses recent work to reconcile Gould and others' ideas on contingency with Simon Conway-Morris' and others' ideas on evolutionary convergence. Really good book!

[Gerrard Farrell]

Re: The evolution of bipedalism

So why would a non divergent first ray and the development of a medial longitudinal arch be of benefit to an obligate biped ?

Perhaps one reason might be because pronation of the foot would allow a more liner progression of the COM during gait with less lateral movement since a pronating foot allows the weight bearing tibial head to move towards the medial sagittal plane .

Any thoughts ?

[Gerrard Farrell]

Re: The evolution of bipedalism

Hi Edmund
A recent press release from South Africa has revealed the fossilized remains of a hominid which dates from about 3.6 million years ago (see link below ) . Called "Little Foot " , the skeleton is almost complete and would have belonged to an animal which still had a foot suitable for living in the trees but walked on the ground as a biped .

So it might be fair to say that the arrangement of the pelvis , foramen magnum and femur needed for bipedalism evolved through brachiation and that the skeletal arrangement arrived at could be used for developing ground up, rotational , high energy kinetic energy in hand held objects .

This leg driven use of tools might have given sufficient advantage to be selected for , resulting in the evolution of a more terrestrial group of hominids with a non divergent first ray in the foot which would be better suited to bipedalism .

So brachiation leads to upright posture giving high energy tool use then commitment to bipedalism ., Simple !


link -Little Foot skeleton unveiled in South Africa - BBC News

www.bbc.co.uk/news/world-africa-42250530


6 Dec 2017 - One of the oldest and most complete skeletons of humankind's ancestors has been unveiled in South Africa. A team spent more than 20 years excavating, cleaning and putting together the skeleton of Little Foot. Its exact age is debated, but South African scientists say the remains are 3.67 million years old.

[Edmund Cramp]

Re: The evolution of bipedalism

With respect, I wonder if bipedalism might not simply be one of those things that “evolved” as a byproduct of other evolutionary pressures?

I was watching the BBC documentary Galapagos the other day and listening to Tilda Swinton describing the “evolution” of different shaped tortoise shells on different islands as “offering an evolutionary advantage” but I just can’t see how that should be the case - clearly, in the Galapagos, size is a significant factor in the ability of the tortoise to survive the variable climate, but the shape of the shell? They are all similar - so assigning this to evolution seems to a bridge too far.

Could bipedalism be the same thing? We’re all involved in biomechanics so we like to think of our human biomechanics as offering some significant advantage but, if it is as good as we think it is, why hasn’t it evolved elsewhere? Other than our chimp family tree, the only other vaguely bipedal animal in the past that I can think of were the Dinosaurs - and faced with an environmental disaster they seem to have found feathered flight far more useful from an evolutionary standpoint. In today's world it's just the Kangaroo, but I can't really see the Kangaroo family as being bipedal in the same way that the first chimps descending from the trees were bipedal. All too often I think we ignore happenstance in Science.

On a lighthearted note, it’s December and so, in the US at least, the Frank Capra film “It’s a Wonderful Life” is being shown on TV again. This always makes me think of Stephen Jay Gould’s book on the Burgess Shale and evolutionary history which has been a big influence on my view of evolution.

[Gerrard Farrell]

Re: The evolution of bipedalism

For those interested here are another couple of posts from the same thread as the one above . They explore the way in which the unshod forefoot functions to provide grip and the causes of the pathological changes seen in the foot when the intrinsic muscles become atrophied . I have included a link to the full thread at the end of this post .


EXTRACT 1
Following on from the posts above perhaps the chimpanzee -human last common ancestor gave rise to a gibbon like phenotype which eventually became terrestrial once more leading to the extant Homo (human) genera of homini . Us

If this happened then the foot of our brachiating ancestors would need to evolve from a grasping structure to something that functions in a quite different way since in my opinion human toes cannot be said to grasp the ground but act to allow traction by remaining straight other than flexing around the metatasophalangeal joints.

Provided at the end of this post is a link to a fossil footprint made about 1.5 million years ago ,possibly by Homo Erectus . You can see that there is a mound of material left between imprints of the toes and the ball of the foot . To me this clearly indicates that even on slippery surfaces the toes of this almost human foot , do not curl but stay straight to maintain traction . The toes do not grasp the ground they remain as straight as possible and presumably hinge around the metatarsophalangeal joints . If the toes curled then the material between the toes and ball of the foot would be extruded giving less grip not more .

Any thoughts

Gerry

https://www.theguardian.com/world/2009/feb/27/earliest-human-footprint-found

Earliest human footprints found in Kenya | World news ...
www.theguardian.com
Footprints found on a sandy plain in eastern Africa have been hailed by scientists as the earliest evidence of modern upright walking. The footprints, dated to ...


EXTRACT 2

Surely with regard to traction the interaction between the substrate and the standing foot is about more than just friction .After all, on a yielding soil imprints are created and within these imprints we find ridges and depressions .
To me this indicates a gravity driven ,passive grip system in the forefoot and also helps to explain the vital role of toe nails in substrate /foot interaction .

The grip system I have in mind will only work optimally if the toes remain straight as the heel of the standing foot lifts from the ground leaving only the ball of the foot and the toes in contact with the ground .

So why do some toes curl during locomotion ?

In brief, in my opinion, the toes will adopt the position of maximum mechanical advantage, for given strength levels in the musculature, when called upon to bare load /produce force during standing or locomotion .

In groups with well developed foot musculature I would predict that the toes will generally remain straight when called upon to perform work. However ,when a foot with weak musculature is called upon to perform work the toes will collapse into hammer or claw toe type positions since it is only these shortened positions that weak toes can perform their roles during gait .

In summary, weakened toes will collapse into the position of maximum mechanical advantage for given strength levels when challenged with load .

In fact I believe this may true of the entire foot with people suffering from pathologically driven atrophy of the intrinsic musculature developing shortened feet with high arches and proximally/dorsally migrated metatarsal /phalangeal joints .

It may be worth noting that this collapsing/shortening of foot structure will ,in my opinion , be most obvious in feet which become weakened but which continue to be subjected to normal loads . If and individual with severely weakened feet subconsciously reduces the load to which the foot is subjected by a change in gait strategy ,for example the adoption of a high stepping gait that avoids toe off ,then perhaps changes in toe/foot morphology are avoided .



LINK TO FULL THREAD

Born not to run but to reproduce | Podiatry Arena

https://podiatryarena.com › Forums › General › General Issues and Discussion Forum



25 Jun 2016 - So why are we the shape we are . Why are feet the shape they are and why is the human scapula configure as it is . Yes they respectively allow us to run and throw but I believe these may notbe the primary driving evolutionary forces . Monolith apart I think Kubrick sums things up nicely in this clip . 2001: A ...

[Gerrard Farrell]

Re: The evolution of bipedalism

Hi Drew
Standing tall ,cautiously , every now and again to see what's about may be a good idea but being permanently upright has been proposed as an a disadvantage in high grasses . This is because if you are head and shoulders above the level of the grass your location would become obvious to predators from long distances .These would then stalk you by remaining low ,in a crouch , below the grasses , as lions etc do .


With regard to the enormous advantages that tool use can provide you might be interested in the extract (below) which I wrote some time ago -( I take the earlier point about modern chimp tool use but to actively hunt in the way described below an ape would have to stand tall and carry a stick along with it . No point in finding prey and then looking for a stick . )

EXTRACT
So is there any consensus between the scientists in the various fields of science involved in studying evolution on the driving forces behind the development of bipedalism in hominids that eventually led to homo sapiens ?

Well my take on it , for what that is worth , is as follows -

The introduction of “biological clock” studies has now puts the split between the lines leading to chimpanzees (pan ) and us (homo) as happening between 10-7 million years ago . It has to be said that some confusion exists over the speed at which this clock ticks ,but lets go with that figure .
So how did our ancestors split away from the lineage of the genus pan and how did bipealism develop ?

Some authorities think that bipedalism developed among a subgroup of great apes involved in brachiation in forest trees with our early ancestors having a gibbon like phenotype ( note they do not say we descended from gibbons but that later more advanced apes became gibbon like through convergent evolution ).

A large amount of work has been carried out on the anatomy of gibbons and the biomechanics of gibbon movement and it does seem plausible that our ancestors developed similar bodies which encouraged bipedal locomotion .
But if such a creature leaves the trees and becomes more terrestrial what evolutionary factors continue to select for bipedalism .
Many ideas have been forwarded for bipedalism and some are listed here -

1 Bipedalism frees up the hands for tool use (Darwin )

2 Hands freed up for males to take collected food back to a chosen location to feed a female and their offspring

3 Seeing over tall grass the better to see predators

4 More energy efficient locomotion

5 Radiation avoidance - a upright stance might reduce heating of the brain

Etc

When considering the first of these proposals ,that bipedalism frees up the hands for tool and weapon use there seems to be a tendency among those discussing the subject to point out that the use of stone tools started only about 2.5 million years ago and that only stick use by early upright hominids might be a possibility . Thereafter in such discussions tool use ( sticks) seems to be rejected in favour of some of the other alternative suggestions for bipedalism .

However I would argue that a gibbon like ape armed with a sick is a totally different proposition than a a gibbon like creature without a stick .

With its bipedal agility and large opposable thumb , a slightly more neurologically advanced gibbon like ape would be able to take a longish stick of suitable weight and , by incapacitating previously unapproachable prey species with the stick, begin to occupy an ecological niche not open to the other great apes .

Such new prey species might include large arachnids ,reptiles and even small mammals .

For example animals such as large spiders and scorpions ,which adopt a static , threatening posture when they themselves feel threatened ,would cease to be food items too hard to tackle and instead become easy to kill with a couple of whacks with a stick .

Its also worth noting that in some parts of India urban rats are still hunted with a simple stick showing how effective this method can be .

Even poisonous snakes ,normally a complete no go for a 10kg ape might be on the menu .

So in summary then early hominids might have evolved a gibbon like phenotype through brachiation and then progressively moved to the ground there hunting with a stick gave them a great advantage over other animals and which allowed bipdalism to continue to be selected for .

[Drew Smith]

Re: The evolution of bipedalism

I think it is very important to consider how much climate and climate change influenced so many adaptations: if the climate changed such that forests became savannahs over a relatively short period of time, then spending more time on hindlimbs surveying above the grasses may have helped to give early warning to approaching dangers, for instance. Being able to take advantage of upper limbs being free to manipulate tools may have just been an added bonus but not the driving force behind bipedalism.

[Gerrard Farrell]

Re: The evolution of bipedalism

Edmund, perhaps a good question ,which I have never seen asked ,might be what abilities would an animal with a chimp like phenotype lose ,or have to a lesser degree , if it evolved into an early obligate biped ? .
Also , what would happen if a group of newly evolved bipeds ( newly evolved from a chimp like ancestor ) found its self in direct competition for territory and food with a group of knuckle walking quadruped chimp like animals ?