Biology 1B Lecture 12: The Emergence of Homo PDF

9/21/24 Biology 1B The emergence Announcements Lecture 12...

9/21/24 Biology 1B The emergence Announcements Lecture 12 of Homo Wed, Sept. 25, Fall 2024 For the Mid-Term review (Monday, 7 pm), submit your questions by noon on Monday (see link on bCourses). FYI, there will be a very simple Hardy- Weinberg calculation on the exam. The Ecology section begins on Friday, 8:10 am with Caroline Williams – and she will run the office hours starting on Monday also. So, this is my last time in person with you all (until the end of the semester)! [L] My last Office Hours is today – no Office Hours on Thursday (I will be in Chicago). 1 2 Biology 1B Study Sleuth Program The Evolution of our Human-ness Program Goals: Open to EVERYONE in Bio1B Help explore lecture content Build a collabora4ve learning community Prac9ce study strategies Logis9cs: What to expect: Starts THIS WEEK! Support and work together to In-person and Zoom learn Link from bCourses for FAQ ⬆ or click here on lecture pdf Welcome to diverse perspec4ves Make space for everyone Take risks! 3 4 1  9/21/24 Questions I would like you to be able to answer for this lecture: Homo erectus developed a unique ability for a primate. What was it? List 4 relevant morphological innovations. Why do we think it Give the approximate times of origin of these intermediates evolved? What was an evolutionary consequence? between us and our last common ancestor with chimpanzees: (1) Sahelanthropus, (2) Homo erectus, and (3) Homo sapiens. Why is Homo erectus reconstructed without extensive hair/fur? It appears that the genus Homo dispersed out of Africa many The human brain grows significantly after birth, increasing the times. When was the first (and what species was it)? When was cost of parenting. List other aspects of human reproductive biology the last (this is a trick question)? that require increased parental investment compared with chimps and gorillas. How does the practice of naming species hide the true nature of the brain-size increase in our lineage? How has our species accommodated this increased cost? How was this solution already foreshadowed with the evolution of hunter- When did tool use begin in our lineage? gathering? The mitochondrial DNA tree of living humans shows that sub- What is the oldest evidence of engravings? Who was responsible? Saharan Africans are paraphyletic. What does this imply about the origin of living people? What is an evolutionary mismatch disease? Give an example. 5 6 The oldest fossils of our lineage now date back to What does the fossil record almost 7 million years, so we have to say about our origins? diverged from our last common ancestor with chimpanzees before then. 7 8 2  9/21/24 The currently oldest fossil of our lineage, the ~7 million-year-old Sahelanthropus tchadensis 9 10 Ardipithecus ramidus ~4.4 million years ago Australopithecus 11 12 3  9/21/24 Australopithecus afarensis Australopithecus afarensis (“Lucy”) (“Lucy”) ~3.2 million years ago ~3.2 million years ago ‘Lucy selfie’, by Élisabeth Daynès 13 14 Emergence of Australopithecus afarensis the genus Homo (Laetoli footprints) 0.002 Ga ago 3.7 million years ago 15 16 4  9/21/24 Homo appears ~2.6 million years ago. Disperses out of Africa ~1.8 million years ago. Homo 17 18 Homo erectus (Nariokotome Boy When did (habitual) tool use [Turkana Boy]) begin (in our lineage)? ~1.6 million years ago Oldowan tools (2.6 – 1.7 Ma), made by Homo habilis 19 20 5  9/21/24 Simple Oldowan tools replaced by more sophisticated Acheulean tools at about the time of the Nariokotome Boy, at the emergence of Homo erectus Herto Man, Ethiopia (160,000 Homo years ago) Homo sapiens Oldowan tools (2.6 – 1.7 Ma), arises 200,000+ made by Homo years ago habilis Acheulean tools (and maybe fire) (1.7 Ma to 100,000 years ago) 21 22 Homo sapiens has a global distribution. When did this happen? 45,000 23 000 190 000 Homo 315 000 From Morocco 195 000 (315,000 + 34,000 years ago) Homo sapiens 115 000 90 000 arises 315,000+ 14 000 800 years ago 23 24 6  9/21/24 Earliest geometric How old are the oldest engravings – Homo sapiens engravings? [of course, it is more than Blombos Cave, South Africa possible that older work will be found] ~75,000 to 100,000 years ago 25 26 How old is the oldest art? [of course, it is more than possible that older work will be found] 27 28 7  9/21/24 El Cas'llo Cave, Spain (~40,800 years old) El Castillo Cave, Spain El Castillo Cave, Spain (~40,800 years old) (~40,800 years old) 29 30 Maros cave, Sulawesi, Indonesia 35,000 years old 40,000 years old 31 32 8  9/21/24 Borneo caves, Indonesia Borneo caves, Indonesia 33 34 Borneo caves, Indonesia At least 40,000 years old Borneo hand stencils between 37,200 – 51,800 years ago) Conundrum: cave art appears on opposite sides of the Earth at about the same time. How did that happen?! Independent origin or is it evidence of the flow of information (mediated by trade?)? 35 36 9  9/21/24 Stunning discovery: earliest geometric engravings Java, ~540,000 to 430,000 years ago So far, we have looked at the fossil record’s story What does DNA analysis tell us? The age and associated fossils suggest this was drawn by Homo erectus! 37 38 Coalescence time (the time of the last common ancestor for the variants of a gene) What are the coalescence times for humans? H. erectus H. sapiens H. erectus H. sapiens Our current genetic Coalescence time variation dates back close to the divergence of our lineage from H. erectus (it may even predate it). 1) Mitochondrial Eve = 150,000 to 200,000 years ago 2) Y-chromosome Adam = 200,000 to 300,000 years ago 39 40 10  9/21/24 Mitochondrial tree for modern humans (traces women) –0 The fossil record and DNA data from – 50,000 modern humans (with paraphyletic –0 sub-Saharan Africans) are unequivocal: – 50,000 Homo sapiens originated in Africa; we are all Africans! – 100,000 – 150,000 With most of the occupants in a given – 200,000 area being polyphyletic, the DNA data Years Mitochondrial Eve before present indicate complex patterns of migration. (was African) 41 42 Brain mass: about 3x what we would expect from other primates given our mass … In what ways are we anatomically unique? 43 44 11  9/21/24 Aside: The practice of naming species hides Homo floresiensis (“Hobbits”) the continuity of brain size increase 90,000–50,000 yrs ago Early Homo erectus (Nariokotome boy) Lucy (Australopithecus) Homo sapiens Ardipithecus 45 46 We are often portrayed as being a feeble species In what ways are we anatomically unique? Anything else beyond brain size? 47 48 12  9/21/24 H. sapiens H. It turns out we are specialist endurance runners, erectus matched by no other primate Innovations for Running (there ~ 20 innovations) Head stabilization Counter-rotation of head vs. trunk vs. hips Trunk stabilization Increased stride length (long legs) Chimp “Lucy” Stress reduction in leg bones Energy storage (Achilles tendon longer) Shock absorption (high foot arch) Stability when foot impacts ground (heel structure) 49 50 Ardipithecus What’s with the loss of fur? Homo erectus (and for most our history, H. sapiens) – the Hunter and Gatherer Hunting becomes a major part of our diet (in part How do most mammals lose heat? because of the nutritional requirements of our large brain) facilitated by endurance running. In turn, the larger brain led to: Increased sophistication of tools Increased pressure for social co-operation (in part because of the possibility of the failure of the hunt; hungry hunters still get fed) Instead, we sweat, and have a huge There was selection on individuals but increasingly number of sweat glands (which on groups – the ‘social being’ emerged don’t work too well with thick fur) Homo erectus 51 52 13  9/21/24 1. Our large brain develops after birth: this puts a heavy burden on the parents (and tribe) Our reproductive biology is also unique (and had evolutionary consequences – increased pressure for social cohesion and support) Here we look at 6 things 53 54 Human reproduction is Most mammal females signal when they are ready to unusual compared with other reproduce (they go into heat) primates! 2. Offspring much more dependent on the tribe (especially parents) – childhood Definition of Childhood: post breast- feeding dependency on others for food 3. Despite requiring more parental investment, the frequency of pregnancies is higher than in chimps and gorillas 4. Females do not go into “heat”, but instead have concealed ovulation (thought to promote increased paternal investment) 55 56 14  9/21/24 5. Older females lose the ability to have offspring 6. Unlike other primates, we “share” our offspring (menopause – the “grandmother effect”) 57 58 Why all this massive investment? Then, with the capacity for 1) Increased energy needs of our large brain; the sophisticated cooperation and brain is only about 2.5% of our mass but uses about 20% of our resting energy. tool use, we slowly 2) It seems likely that social cohesion, and later transitioned from hunter- language and culture, probably played a gathering to agriculture major role in determining which groups were able to pass their genes on to the next generation (this is called “group selection”). 59 60 15  9/21/24 The Development of Farming (starting ~10,000 years ago, but Ifugao Rice Terraces, Philippines (maybe 2,000 years old) village life began ~20,000 years ago, for example in Jordan) Begins after well after the last ice age Enables support of larger populations Radically changes our ecology 61 62 Longji Terraced With Agriculture: Rice Fields China Can accumulate surplus (wealth). (but these are Need to account for surplus (motivation for writing?). quite young, only about Can build religious structures. 650 years ago) Can store material objects. But after a while can’t go back to the hunter-gatherer lifestyle because population increase leads to too many people to be supported by hunter-gathering. And it leads to famines, loss of height, and a whole suite of new diseases … (next slide). 63 64 16  9/21/24 Non-infectious mismatch diseases But now with easy access to high 99.5% of Homo’s history (beginning with H. erectus about energy foods and reduced need to use 2 million years ago) was dominated by the selective pressures associated with finding scarce food, hunting and our bodies, this evolutionary strategy is gathering, including endurance running. leading to an obesity crisis, which in Then with agriculture and later industrialization, we turn leads to increased: changed the way we use our bodies and our nutrition. As hunter gatherers high energy foods are hard to come Type 2 diabetes by – we evolved ways of storing surplus by putting on fat Heart disease, stroke – gaining weight when there is excess food is a wonderful High blood pressure evolutionary strategy. And others (see the WSAQs) 65 66 v v These are called noninfectious mismatch diseases, because of the mismatch between Rise in obesity our current lifestyle and our deep over the last evolutionary history. Treatments can be 30 years developed by paying attention to how we evolved, therefore how our bodies and minds have been honed by natural selection, and BMI > 30 how our current lifestyle is at odds with how our bodies and minds work. An evolutionary view has really important health implications! 67 68 17  9/21/24 What’s next? Natural selection This 1st section of the course has plays out in the introduced you to biology’s evolutionary arena of ecology principles And so the 2nd As we have seen, natural selection is the section of Biology process that leads to adaptation, to the 1B will be on ‘tuning’ of the characteristics of organisms ecology led by to their environment Caroline Williams 69 70 Can you recognize the: Here it is, our entire history in 90 seconds Big Bang [And a question for you: can you remain open to the wonder of it all, Formation of the stars and galaxies and think sensibly about it at the same time? I find this very hard] Formation of the Solar System (the Sun and Earth) Formation of the Moon Formation of the oceans Origin of life Origin of photosynthesis (green cells) Origin of the first animals (Ediacarans) Cambrian explosion (a trilobite) First vertebrates Vertebrates reach the terrestrial realm Dinosaurs End Cetaceous Bolide impact at Chicxulub Mammals emerge from the mass extinction Primates emerge … and the rest is history (as they say) … http://www.youtube.com/watch?v=ZSt9tm3RoUU 71 72 18  9/21/24 I hope you have learned some things of interest! Wishing you the best in the shorter term (e.g., in Biology 1B), and in the longer term – may you all learn to live well according to who you are! I will miss you all!! 73 19