Which hominin species were the Croods?

To celebrate finishing our human evolution unit bookwork in biology, we have been watching The Croods. We were then tasked with deciding which hominin species The Croods are, and justify why.

Biological evolution

Looking at Grug, the Croods father, he has a low-sloping forehead, prominent brow ridge, and strongly built jaw, all of which are features of the Homo heidelbergensis skull, who lived between 600 and 200 000 years ago. The large fleshy nose and comically large teeth are also an indicator of H. neanderthals.

Efficient bipedal walking was clearly demonstrated by all of the Croods in the film which the H. heidelbergensis was well adapted for, this suggests the Croods weren't ardipithecus ramidus, australopithecus afarenis, australopithecus africanus or paranthropus boisei, who were not fully bipedal.
The Croods hands featured short and straight fingers, opposable thumbs and dextrous fingers, suggesting they fit into the hominin timeline sometime during/after when H. habillis existed. H. habillis had the human-like ability to form precision grips, evident in the Croods when they held objects, small stones, made cave art, etc. 

Cultural evolution
The cultural evolution of the Croods is strong evidence of neanderthilic behaviour, in that like the Croods, neanderthals wore some animal hides as clothing, they were also able to control fire for warmth which was demonstrated by Guy's ability to make fire, eventually Grug's (Grug learning to make fire from Guy is a great example of cultural evolution). One big example of cultural evolution was the Croods consistently making cave art, which is first correlated with the H. neanderthals. 

Language wise, The Croods speak at a very very complex level of modern language, more developed than the neanderthals and more like like H. sapiens, who are able to communicate very very well, are socially coordinated, which the Croods clearly show. They are creative and have the ability to build traps, suggesting a level of complex and abstract thinking, like H. sapiens do. The Croods also domesticated animals by the end of the film, a big indicator of H. sapien behaviour (yet they lacked the agriculture knowledge that actually lead to the domestication of animals in reality). 

Overall looking at the Croods I think they are a mix of H. neanderthals and H. sapiens culturally wise, however, there they show diverse traits of earlier hominins and there are some 'gaps' in their knowledge, eg. not knowing how to make fire, living in caves, etc, yet they are still able to communicate at such a complex level, are wearing clothes, etc. Visually, they have retained a lot of early hominid skull features- low, sloping forehead, large noise, strongly built chins, and were rather short, all features of the H. heidelbergensis. 

To conclude, considering The Croods is an animated film, I don't think it's really going to be all that accurate when it comes to biological/cultural evolution of hominins, but it was still entertaining to watch. 

The cultural evolution of death and spirituality

It was in the time period where neanderthals and homo sapiens began to roam the Earth that evidence of art and spirituality began to appear, suggesting that hominids had shifted from trying to stay alive through finding food and shelter, to now having the time and brain complexity to be thinking more abstract thought and performing spiritual and symbolic rituals, such as burials. There is evidence of these mass burial sites spanning back to the Palaeolithic period, when the neanderthals lived. However, it is difficult for archeologists to determine whether these burials were intentionally made, whether there was abstract or 'higher' thinking surrounding them, etc. 

For example, in the Shanidar Cave in Iraq, the fossils of at least 10 neanderthals were discovered and are believed to date back 60,000-90,000 years. What made this discovery initially groundbreaking was the appearance of pollen alongside the fossilised skeletons, which made archeologists suggest flowers were placed beside them during burial. If true, this meant neanderthals were possibly capable of abstract and symbolic thinking, up to 90,000 years ago. Some scientists suggest that later hominids may have returned to the burial site to place the flowers later, or that it was actually mice who carried in traces of pollen from the outside environment into the burial site. So, scientists are still unsure whether these skeletons were buried intentionally with ritual or not. 

In a cave in Atapuerca, Spain, nicknamed "the pit of bones", 600,500 bone fragments were discovered, of both animals and 28 hominins, believed to be of the Denisovan species. These fossils are believed to be at least 300,000 years old and may be as old as 600,000 years. Lack of evidence suggesting a flood or ground collapse that would have trapped the individuals in the cave have lead scientists to believe that these denisovan individuals were intentionally placed in the cave after their death. However, we don't know the reason why. The individuals may have been put in the cave after they died to remove the smell of rotting flesh, or to stop the corpses from being eaten by predators. Or, the individuals may have been diseased, and put in the cave to avoid transmission, but this would suggest these hominins had knowledge of disease transmission in the first place: due to the brain size of the denisovans, this is unlikely. But while they may have been placed there intentionally, the skeletons of these individuals were not arranged in the cave, which doesn't suggest a burial ritual happened. 

However, in 2013, The Rising Star Cave in South Africa, the remains of fifteen Homo Naledis, dating to around 250,000 B.C were discovered. The remains were located in the 'Dinaledi Chamber', which could only be accessed through the 'Superman's crawl' and 'The Dragon's Back', stretches of cave which were only around 1ft tall. What is interesting about this site is that each of the remains were placed there gradually, over time. Scientists agree that while the Dinaledi chamber was used to dispose of the dead, they do not all agree that the cave is a definite burial site, where the skeletons were buried intentionally and with ritual. There is no evidence of symbolism that suggested higher thinking in these hominins, and the individuals could have again been placed there to remove the smell of rotting flesh, or to stop the corpses from being eaten by animals. 

It was in the Qafzeh Cave in Mt. Precipice, Israel, that 15 skeletal remains dating back to 92,000 B.C were discovered. These fossils were of very early homo sapiens, buried alongside flint tools, seashells, and red ochre clay. What's interesting about the burial of these remains is that some of them were buried in an orderly fashion within the floor of the cave, rather than, for example, the "pit of bones" where remains seemed to be just dumped there in no particular arrangement. Two of the skeletons had deer antlers in their hands and some bones of the remains were coated in this red ochre clay: this is important because it suggests some aspect of symbolism, some higher thinking in the homo sapiens who buried them, as well as ritual and burial preparation. Since it was the bones coated in red ochre, and not flesh (which would not have been discovered in the fossil record), this indicates people went back to the burial site, perhaps to grieve these individuals. The tools they were buried with suggest homo sapiens could have had some form of belief in an afterlife, that these individuals would need the tools later. These discoveries at Qazef cave were really significant because it shows evidence of such profound cultural and spiritual evolution in homo sapiens by 92, 000 B.C. It indicates hominins were beginning to instead devote their time to more abstract and 'higher-up' thinking, signalling a shift from living to purely survive, to living for more abstract, perhaps religious, and more 'recreational' purposes. From there, homo sapiens continued to evolve culturally, moving onto cave paintings, the development of agriculture, permanent settlements, and eventually, more complex burial rituals, like those of Ancient Egyptian mummies. Today, every single culture on Earth have their own special burial rituals. I find it so interesting for us to be able to look back and see when and how our own archaic ancestors started it all. 

The Link Between Maltreatment in Childhood and The Development of Borderline Personality Disorder by Jaime Burns

Borderline Personality Disorder, also known as BPD, is estimated to be present in 1.6%, or approximately four million people in the United States population alone [Chapman, 2021.], yet the disorder continues to lack sufficient scientific and psychiatric research. Out of the disorders’ many complex aspects, perhaps one of the most important in my eyes, is what impact the nature of ones’ upbringing and early development has on one's' potential development of Borderline Personality Disorder later in life (in which adolescence is marked as a significant period for symptoms to become apparent). Maladaptive parenting, sexual abuse and one developing in an overall adverse family environment has been, and continues to be, implicated in psychiatry as some significant environmental factors that evidently, may precede a personality disorder diagnosis later in life. Trials show many borderline-diagnosed individuals recall some forms of childhood maltreatment, including but not limited to sexual abuse, low warmth from parents, and harsh punishments in their development, at much higher rates than those of the healthy individuals against which they were compared to. [Steele, 2019] This report will evaluate and challenge these scientific and psychiatric findings relating to sexual abuse and maladaptive parenting (specifically low warmth from parent and harsh punishments) as possible mediating factors preceding ones’ diagnosis of Borderline Personality Disorder later in life. 

Borderline Personality Disorder, also known as BPD, in abstract, is recognised for the abnormal, fixed patterns of thinking it causes, significantly, ones’ intense fear of real or imagined abandonment, which as a direct result may lead to recurrently unstable interpersonal relationships. Emotional disregulation is also a significantly-recognised symptom in those diagnosed with the disorder. Many patients have been recorded to display frequent, wild, and intense emotional reactions, often disproportionate to the preceding event. The Diagnostic and Statistical Manual of Mental Disorders (DSM) identifies 5 of 9 of the following criterias are required to be met for ones’ diagnosis of borderline personality disorder: chronic feelings of emptiness, unstable emotional reactions to day-to-day events (this may include periods of sadness, anger, numbness, etc, all of which are generally severe in intensity, lasting anywhere from a few minutes to days), frantic efforts to avoid real or imagined abandonment, persistently unstable sense of self and self-image, impulsive behaviour (eg. hypersexuality, substance abuse, overspending), difficulty in controlling anger, which may be extremely intense and frequent, significant patterns in unstable and at times, intense interpersonal relationships, recurring suicidal ideation, self-harming behaviours and/or attempts at one’s life, and symptoms of dissociation. It is also important to recognise ‘splitting’, which is not listed as an actual symptom of the disorder, but is instead a subconscious coping mechanism commonly used by Borderline individuals, especially in periods of stress or intense emotion. Splitting is typically periodic, and causes one to view all aspects of their life, including people, in extreme absolutes- ‘black and white’, or ‘good and bad’: there is no inbetween. While used as a coping mechanism, splitting significantly affects one's emotional responses and reactions, and can be exhausting to both the borderline individual and those around them: unstable relationships remain one of the most commonly-reported symptoms in patients.

Borderline Personality Disorder, evidently, has many factors that precede a diagnosis later in life: there is an increased likelihood of offspring inheriting the disorder from a parent with the disorder, some studies showing over 50% inheritability [Amad, A., Ramoz, N., Thomas, P., Jardri, R., & Gorwood, P. (2014)]. From my own view, it could be important to take into account that parents with Borderline Personality Disorder can actually produce children with the disorder not through genetic predisposition, but instead through maltreatment in the childs’ development, and statistics on this could be skewed: genetics may be assumed as the sole preceding factor for a childs’ diagnosis, if negative early environmental factors are not discussed, are disregarded, or unknown. Nevertheless, environmental factors, particularly in childhood, continue to be heavily implemented in psychiatry as a factor in the development of Borderline Personality Disorder. This report specifically discusses the following environmental factors: low warmth from parents, harsh punishments, and sexual abuse. ‘Low warmth’ may refer to using shame, hostility or ridicule against a child when in times of high psychological stress, eg. during temper tantrums, when unable to sleep, when sick or injured. The child, instead of being provided care, support, and healthy ways to cope with the situation, is instead having their emotions invalidated and disregarded; they are essentially being told to hide them away. This is just one form of malaptative parenting that may lead to emotional dysregulation. According to US psychologist Marsha Linehan’s 1993 (updated in 2009) biosocial theory of Borderline Personality Disorder, emotional dysregulation is a core symptom of the disorder. Linehan theorises the disorder stems almost entirely from emotional dysregulation, which emerges from ‘transactions between individuals with biological vulnerabilities and specific environmental influences.’ [Linehan, M. M. (2009)]’. However, here I believe it necessary to note that emotional dysregulation is merely one symptom of the disorder: it should be recognised that while yes, a child can very well develop emotional dysregulation due to maladaptive parenting, the disorder in it’s entirety hasn’t necessarily developed. 

Harsh punishment from parents is a significant environmental factor implemented as a mediating factor in the development of Borderline Personality Disorder. According to M. A Straus’ 1998 Parent-Child Conflict Tactics Scale, a scale created and used to identify maltreatment between parent and child, parent disciplinary practises can be divided into five categories. The first category is classified as ‘non-violent’ which may include removing privileges, or explaining why something is wrong.Non-violent disciplinary action is deemed to be positive and healthy for a childs’ development. The second category is classified as ‘psychologically aggressive’, which may include yelling or name-calling, and the third category being ‘physically violent’, which includes physical abuse: hitting, slapping, or beating a child (this includes the widely-used practice of spanking). The fourth category is neglect, defined here as: The fifth category, which we will discuss further in detail later in the report, is reserved for sexual abuse, which the scale defines as “unwanted sexual touch” and “forced sexual contact”. In this report, I will refer to actions under categories ‘psychologically aggressive’ and ‘physical assault’ as harsh punishment; these may include verbal acts by the parent which ‘cause psychological pain or fear on the part of the child [M. Straus, 1998], such as yelling, swearing, using threatening words, etc, as well as physically-harmful behaviours, which range from low in severity (spanking) to high severity (punching, kicking, slapping, etc). Any form of these behaviours performed against a child may be detrimental to their development: growing evidence in psychiatry supports the fact there is a significant link between a range of the above actions and the development of Borderline Personality Disorder later in life. A trial led by S. D Stepp, conducted to explore ‘bidirectional effects of parenting on the development of BPD symptoms in adolescence’ [Stepp, S. D., Whalen, D. J., Scott, L. N., Zalewski, M., Loeber, R., & Hipwell, A. E. (2014).], specifically examined the impact of child-reported harsh punishment practices in 2,451 adolescent girls (aged 14-17) diagnosed with Borderline Personality Disorder. The trial was concluded to have found a ‘moderate’ association between symptoms of Borderline Personality Disorder and parental behaviour that included the use of harsh punishment and low warmth. I find it important to mention that this trial referred to the Conflict Tactics Scale to identify which actions can be classified as harsh punishment. For one question in the trial, girls were asked to report on how often they experienced harsh punishment from their parents in the past year, referring specifically to the actions of shouting, yelling, screaming (psychologically aggressive behaviour) as well as spanking (moderately severe physical assault). The Stepp trial was concluded to have found evidence relating the girls’ elevations in their BPD symptoms within one year to elevations in the use of harsh punishment and low warmth from parents in the same time period, therefore suggesting a relationship between these forms of maltreatment and the development of Borderline Personality Disorder later in life. An important acknowledgement that should be made is that this trial only supports specific forms of maltreatment, low warmth and harsh punishment, and therefore should not be used as evidence to justify any other forms of maltreatment as a mediating factor of Borderline Personality Disorder: other actions were not explored and therefore cannot refer to Stepp’s report as evidence. Another acknowledgement, or rather a personal problem I have with these statistics is that the trial was merely child-reported: ones’ recorded experiences with their parents are simply taken for word; there is no way to determine if the victims are telling the truth. In a disorder where negative or unstable relationships with family, including parents, are incredibly prevalent, it is important to acknowledge that the childs’ responses may be inaccurate or exaggerated, possibly to paint their parents in a bad light, and therefore could result in inaccurate data and false conclusions. Furthermore, the Stepp trial took data solely from adolescent girls (aged 14-17) - the evidence taken does not necessarily reflect other age groups, nor males with Borderline Personality Disorder. These acknowledgements made, I do think this trials’ evidence is useful and rectifies my belief that there is a moderate link between the maltreatment practises of harsh punishment and low warmth in childhood and the development of Borderline Personality Disorder later in life. 

Another form of maltreatment in childhood that has been identitfied in psychiatry as a possible mediating factor in ones’ development of Borderline Disorder is sexual abuse. The implication that sexual abuse and borderline personality disorder are linked makes me curious, as I personally wouldn’t say I know enough information about the subject, and the link between the two is not as obviously clear to me, at least compared to the other two factors (low warmth, harsh punishment) included in this report. To my surprise, the studies I researched had contradicting conclusions. A 2013 cohort study conducted by Marina A. Bornovalova studied the link between seuxal, emotional, and physical abuse in childhood and Borderline Personality Disorder traits at age 24. ‘Sexual abuse’ in this specific trial refers to two questions participants were asked: if they ‘had sexual contact with anyone five or more years older than him/her before age 13, and whether anyone (friend, relative, etc) ever used pressure, force, or physical threats to make the participant engage in some sort of unwanted sexual contact.’ [Bornovalova, M. A. (2013).], sexual abuse in this trial was specifically defined to include any form of sexual exploitation under the age of 18. To my surprise, the trial’s results actually show more evidence linking genetic deposition as a more significant mediating factor compared to the various forms of child abuse the trial explored (emotional child abuse, physical child abuse, and sexual child abuse). The trial concluded, “Genetic factors accounted for most of the association between BPD and CA.” [Bornovalova, M. A. (2013).] Furthermore, I learned these results were consistent with another clinical trial, Distel et al. (2011), which also concluded that genetics are a more significant mediating factor in the development of Borderline Personality Disorder rather than exposure to traumatic events. It’s important for me to note here that these trials did not specifically focus on sexual abuse as a possible mediating factor, but a range of traumatic life events, including but not limited to: divorce, violent assault and sexual assault. However, the results were intriguing, and give me the idea in my mind that possibly exposure to early traumatic events (which I deem to include sexual abuse, harsh punishment, and low wamrth) in childhood, could overlap with genetics as mediating factors in ones’ development of Borderline Personality Disorder. The conclusions of these two clinical trials contrast to other publications I researched. A 2018 systematic review published by Dr. Lucas Fortaleza de Aquino Ferreira, “Borderline personality disorder and sexual abuse: A systematic review”, which reviewed 40 papers based on the link between sexual abuse and borderline personality disorder, attributed sexual abuse to play a major role in the development of the BPD patients studied- particularly women. Moreso, Ferreria established that BPD patients with a history of sexual abuse presented more severe symptoms of the disorder, such as self-harm and dissociation, as well as PTSD (post-traumatic-stress disorder). [de Aquino Ferreira, L. F. (2018)]. Another finding of research I looked into was a study investigating reported pathological childhood experiences associated with the development of Borderline Personality Disorder, conducted in 1997 and led by M C Zanarini. ‘Pathological experiences’ included emotional abuse, physical abuse, sexual abuse, and neglect: while sexual abuse by a male noncaretaker (along with emotional denial by a male caretaker, inconsistent treatment by a female caretaker, and being a female) were concluded to be predictors of a diagnosis with Borderline Personalty Disorder, the trial concluded that experiencing sexual abuse in childhood was “neither necessary nor sufficient for the development of borderline personality disorder”. [Zanarini, M. C. (1997)] With all of my research findings combined, I find the link between sexual abuse and the development of BPD weak and unresearched, although diagnosed patients may have a history of sexual abuse in childhood, many also experienced other forms of abuse such as physical and emotional abuse; to me, there is simply not enough strong, clear and defined research for me to to say I believe sexual abuse is a predictor of a Borderline Personality Disorder diagnosis: I think it would be more harmful to do so.

From my research into these clinical trials, systematic reviews, and other psychiatric findings, I have come to the personal conclusion that there is a moderate link between the maltreatment practises of harsh punishment and low warmth and the development of Borderline Personality Disorder, and a weak-moderate link between sexual abuse in childhood and the development of Borderline Personality Disorder. I’m also further interested in investigating the possibility that these mediating factors, and ones’ genetic predisposition, could overlap with one another into ones’ development of the disorder. I do wish more research is undertaken to more clearly establish this. I believe psychiatrists should aim to establish a more clear understanding of the parenting practises- deemed harmful or not- in Borderline patients, to continue to strengthen presently ‘moderate’ links between harsh punishment, low warmth and sexual abuse in childhood and the development of BPD later in life. Not only that, but psychiatrists could also implement the practise of delving into patients’ genetic predispositions to the disorder, by acknowledging not only the parents mental health history, but that of grandparents and siblings. Coinciding with the patients’ early childhood circumstances, i.e identifying forms of possible maltreatment that have occurred, these practises will be helpful in that it helps psychiatrists be able to draw a firmer, more-defined conclusion on the link between maltreatment in childhood and the development of Borderline Personality Disorder, a link I personally consider to be moderate. 

Hunting/gathering lifestyle vs. an agricultural lifestyle

Before the last glacial maximum of Earth around 20 000 years ago, humans were living a hunting-gathering lifestyle. Using advanced projectile weapons such as bows, arrows, and spears, coinciding with advanced intelligence and good communication skills, humans became excellent hunters. However, this lead to many of the Earth's large animals being killed off. 

This was not the only disadvantage to the hunter-gatherer lifestyle that humans used for many years.

• Finding animals to hunt and then actually killing them took lots of time and energy for humans. This meant they couldn't focus on other things that would've helped them develop eg. cultural development. 
  
  
  
• Humans couldn't carry many belongings on them because they were always on the move: everything they owned, they had to carry.
  
  

There were some advantages to this hunter-gatherer lifestyle.

• Less resources and land were required to gather food. 
  
  
• There was reduced transmission of diseases, as livestock weren't held in captivity/in close range to each other to allow for disease to spread far. 
  
  
• Since humans had to always be on the move to find animals to hunt, there was less exploitation of the resources of just one certain area, meaning there was less pressure on the species inhabiting that area.
   
• There was less reliance on just 1-2 limited food sources, they could hunt a variety of lean and fatty meats from different animals which did provide good nutrients. 
  
  

However, around that 20,000 k.y.a mark, Earth went through a significant climate change where it became warmer, forested areas and grasslands become more prominent: the region became more favourable for human living. As a result of this, they could live in one place at a time and form simple settlements. With the killing off of many large animals happening at the same time, the first evidence of agriculture appeared in this time period.

A settled, agricultural-rich lifestyle provided many advantages to humans.

• For one, less energy was required, since humans didn't have to go travelling for miles finding their prey to kill. Instead they could stay in one spot, their simple settlement, and use that energy towards other useful activities. Farming gave humans the time for reproduction, increasing populations and therefore protection from predators, and cultural development: i.e learning about farming, developing new and better techniques and technology, and sharing that knowledges with others in their settlement: role specialisation and division of labour would've started to be used for more productive farming as agriculture become more prominent. 
  
  
• Farming provided humans with a steady and high quality food supply.
  
  
• Humans no longer had to rely on 'mass kill sites' for meat, which would have often went to waste if it wasn't eaten quickly enough due to rot. They could kill exactly however many animals they needed to feed settlements at a time and not waste food.

However, changing to settled and agricultural rich lifestyles also had it's disadvantages:

• Natural disasters could wipe out entire crops at a time, meaning entire settlements could lose most or even all of their food supply. 
  
  
• Nearby settlements or other humans could easily come and steal crops and harvests.
  
  
• Lots of animals living in very close proximity to each other increased the risk of disease transmission spreading quickly through livestock.

Despite these disadvantages, agriculture was one of the greatest developments in human history because it supported large populations of people living in settlements and eventually villages and cities, lead to the technological innovation such as the invention of the wheel, plough, hoe etc, helped introduced trade, and the domestication of animals, helping humans move up and eventually dominate the food chain, and Earth itself. To this day, we rely so heavily on agriculture without even necessarily realising the full extent to which we do. 

Potatools

 

In Biology we have been learning about hominid development as part of the human evolution topic. One topic we have been focusing on recently is stone tools, which are obviously a key part of hominid adaptation and development. 

There are four main types of stone tools, increasing in complexity as time progressed:

-Oldowan tools were associated with H. Habillis around 2.7-1.7 million years ago. They were fashioned by striking two stones together 5-6 times to produce a sharp(ish) edge.

-Acheulian tools were associated with H. Erectus and H. Ergaster. These tools were more complex, fully shaped, required more planning and were often teardrop shaped. They took around 50 blows to make.

-Mousterian tools are associated with Neanderthals, produced across much of Europe, Asia and Africa around 600 000- 400 000 years ago. They were much more complex compared to oldowan tools as they required more than 150 blows. Flint was often used because it flakes in a predictable manner, making the tools easier to make and craft. It reflects on the hominid brain quickly developing and becoming more intelligent.

-Finally, upper paleolithic tools are associated with H. sapiens beginnign around 50 000 years ago. They required more than 250+ blows and are very complex, use a variety of material, and reflect on the very intelligent human brain. 

Mitochondrial DNA and Human Evolution

In 1987, geneticists Allan Wilson, Rebecca Louise Cann, and Mark Stoneking published the article "Mitochondrial DNA and Human Evolution", in which they showed that all modern, living humans can be traced back to a single woman living in Africa, approximately 100-200 000 years ago, later coined 'Mitochondrial Eve'. They found this evidence by sourcing mitochondrial DNA from 147 humans, living in vastly different areas of the world- Asia, Europe, New Guinea, Australia, Africa, from placentas. Mitochondrial DNA differs from 'regular' DNA in that it is only passed down maternally, from mother to daughter, and does not recombine during meiosis. This means it doesn't change between offspring aside from mutations- however, the geneticists found that the mutations occurred fairly consistently and were able to actually use them to their advantage, like a 'biological clock' where they could get an accurate idea of the timeline and trace the lineage of the shared mtDNA way back until they found this last common ancestor, the "Mitochondrial Eve". The "Mitochondrial DNA and Human Evolution" article suggests this single woman's bloodline or 'lineage' by chance, survived over all other lineages, was continually passed down from mother to offspring, not changing aside from mutations, and expanded all over the world to eventually be present in every single currently living human's mtDNA. 

Source:

Haskett, D. (October 10 2014). "Mitochondrial DNA and Human Evolution" (1987), by Rebecca Louise Cann, Mark Stoneking, and Allan Charles Wilson. 

Retrieved from: https://embryo.asu.edu/pages/mitochondrial-dna-and-human-evolution-1987-rebecca-louise-cann-mark-stoneking-and-allan

Art 2.3 internal (I finished my board!)