Chimpanzees and the Evolution of Human Life History

without mental pansies from Harvard University and physiology history ready physiology lots of researchers to I’m very happy Cherokee girl and humans to understand eh Oh Peter at all um most of my research involves trying to stand how the environment influences of physiology of great apes and subsequently how that influences of social behavior so today I want to repackage a lot of the work that I’ve done in the context of how we use what we know about chimpanzee reproductive biology to help understand some of the transitions that have occurred and the evolution of her unique human like the string so as you all know the rural population is one of the related problems in the world today this is largely driven by fertility rates in developing countries that are on the range of 68 I’ll spend her family’s even higher and while overpopulation itself is certainly a moderate problem Ministry of our species is one of rapid expansion into lots of territory basically all the territory the earth has to offer meanwhile we’ll look at great apes in both Asia populations are declining to secure matically and the reasons for these declines are surprised they’re largely human-induced causes deforestation human diseases hunting how are you flip side of that is that these populations have very difficult to recover from those kinds of insults because of relatively low fertility rates and so here even in the chimpanzees in well study well protected communities most females are giving birth to only 34 offspring in the lifetime when we factor in infant mortality for even these well protective populations many are reproducing at a replacement level and in fact any two passing the floor in the Wyoming has about a fifty percent chance of reaching earth reduction itself so as the primatologist looking at what is a very typical picture of a traditional human family there are lots of surprising things here primarily the large number of children that are closely spaced together that are all very highly dependent on the mother even the oldest child this picture is far from reaching the age for yourself and then you have also a grandmother here who’s helping you to to provide for this group of children so my question is how did we get here from there from our closest living evolutionary relative what we consider to be the best model for our last common ancestor species that takes a lot of time and effort and care for its offspring yet only produce them at a very slow rate chimpanzee so today we’re star wars are talking about general life history of party for those who are unfamiliar with it we’re going to talk about a range of studies will introduce a general methods in the field side in the lab work that I do talk about our purpose cities that attack different aspects of fertility

differences between the two species and then just stopped briefly about some future work and life history so for quite a lot friends people use private life histories in order to try to understand the changes that occurred during human evolution and this diagraph from Schultz showing key structural properties of primate life histories that’s probably been reproduced hundreds of times in different contexts that it shows some of the variation that occurs across primate species but also highlight some of the unique features that humans have which include extended juvenile dependency and overall much longer lifespan we predict for a Norina some of our size and this includes / women a substantial post reproductive period and so in fact they reproductive period between us into frenzies doesn’t look that much different now these structures of life history have processes underlying them and they can be understood within a fairly basic life history framework and the simple rule here is that energy for organisms living natural environments is limited and it has to be divided between various processes in a way that ultimately leads to reproductive success so organisms that want to invest heavily in producing babies have to do so at the expense of survival enhancing it to these things like fat storage immune function and cellular repair and the reverse is also true organisms that would liberal month I generally have to do so at the expense of reducing and so these these kinds of decisions about how to Ella community there are species hundred properties as well as individual variation that’s all okay so we are just have a comparison of various primate species as you can see some of the variation in reproductive properties so we go through some very small species like the lemurs lorises some of the neotropical projects are also quite small up to large primates like the great apes and humans and as we go up in size a lot of teachers of reproduction change you’re producing a larger offspring that has to get to eat a large signs and for Apes and humans in particular you’ve got an additional costs associated producing a disproportionately large brain and because apes are are a big animals they already have their budgets so amassing a little bit of extra energy it needs to care for an infant build a baby is really quite costly expense so one of the things that would tend to see one of the things that we tend to see as privates get water is that the reproductive period extends of disproportionately you see longer the station links Lowry lactation periods accompanied by a slower romantic growth and what this basically strategy for from the mother to invest less proportionately less of her daily energy budget towards that in events I think Spence of taking over and humans clearly bought the trans here it comes to their period lactation of the birth interval whereas chimpanzees have birth intervals of around five or six years in the wild humans and to gather populations are able to reproduce about any three or four years to say producing more expensive infants so I’m not going to pretend that this is is a particular puzzle we have lots of good ideas about how humans have managed to accomplish this by gain more energy from their environments and by sharing the burden of infant care but I want to point out that this is actually kind of a puzzle because when we look at the reproductive biology of humans we see it an extraordinarily conservative approach towards conceiving infants humans are one of the rare species that experiences we were non-consent of cycles than consumptive cycles so where is the lemurs we saw the previous slide they only once per year it may only make one day out of the year in some cases I may conceive daughter every time humans and populations around the world take on average several months and in order to conceive this is a highly conservative pattern and it’s one that reproductive ecologists like Peter Ellison and his students and colleagues of attributed primarily to management of energy consistent with that leg mystery framework and they have found through a

variety of naturalistic and experimental studies that women are highly sensitive to their current energetic condition in particular energy balance which means gaining or losing weight or energy expenditure when you pass it use a high calories during your daily activities they study this quite extensively using ovarian hormone measurements and so they can look at the Russian of estrogen is just row during the course of the site how that responds to different energetic conditions so for example here you have a study showing that women who lost the moderate amount of weight produce less progesterone direct cycles than throw women and this would it was also the reduced ability for a penis to actually plan to the endometrium so the nice thing about these studies a little additional things that this peter also has actually put this into a nice adaptive framework and the idea is that these cons of energetic signals are signaling the abilities actually character an energetic pharisee energetically costly reproductive effort and if a woman is losing weight she’s unlikely to be able to properly adjust the atlantic an infant so it’s better to make that energy use it in the future at the time and the next thing about this large body of work from human reproductive ecologists is that it provides a really good model of which to compare of species the problem is really lack of data on other credit species so I think we can go from his kind of gross like this tree structure comparisons and really better understand the evolution of human life histories by aiding better data on these other species exploring the variation and let the street patterns with him species as has been done for humans and try to understand the processes that are actually going on at these different life history transitions the processes that under variation histories so these are kind of guiding principles for my research this establish what foundation on which the human life history has evolved from what what’s wait life is really look like in a while what processes drive variation and let history patterns and all this process is actually derived from Newman’s or do we use basically the same energetic allocation strategies to sing like history strategist just in a vastly different context so if never colonists were often pointing to similarities between humans and chimpanzees and there’s certainly some of these like the very large five size the complex diet and the extended period of offspring dependency then we might expect to drive these two species towards similar reproductive adaptations on the other hand is this reproduction is placed in a really different context so for chimpanzees so the species is highly promiscuous for any given birth a female makes hundreds of times and usually with all the male’s of your group roles to all of them at the male’s provide essentially no maternal care and really was little provisioning of any kind in a wild chick fancy community whereas a mother role of course recipe for offspring she rarely provides any direct provision for offspring outside of that context so our challenge here is in gaining the kind of detailed data that we got four humans from well primates of course we humans you can ask them typical examples for you weigh them as often is like you can even change their exercise regimes are their diets and we can do some of these things for Captain projects but can we be missing all the good stuff put all the stuff about your fluctuations and energy in their environment the amount of energy it cost them to gain or nearly calorie needs things like living on our social group which create food competition and so we really need to study this in the wild and here we have the problem of an organism that lives in very large power ranges inflexible social groups so it’s difficult phylum females are less gregarious than males so they’re even harder to find and once you finally we need to be able to obtain my life samples without actually interfering with their activities are positive or stress and in order to study figure out reproduction in a species that reproduces so slowly if you want to get information from one birth to the next it requires many years of study so I’ve been fortunate enough to work with the project this challenge in getting long-term integrated data on the behavior of community of chimpanzees as well as getting biological samples to perform of

urine from these chimpanzees on and basically as often as possible this cabal extreme fancy project was established by Richard Wrangham of arbor university it makes me seven it’s currently a co-directed by Martin Muller a few NM this looking at here at south western Uganda and the Cabal a forest and as a part of daily david collection the field systems not only collect basic data on the food availability social behavior etc they collect every gram sample that they can and so since 2000 i’ve been involved with this project and after doing some field work I’ve been chiefly responsible for managing a large collection of physiological samples and to the analysis of these samples so right now we have over 25,000 here at samples collected from 94 nitrogen penzeys and most of my time these days that not revealed laboratory during a variety of biomarker and Elsie’s these are not all things we can do in chimpanzees many of these the things that we do with our collaborators who are studying humans now but my love specializes in getting physiological information from non-invasive media so for human it’s a lot of primates escape in feces or urine and all these things some of these are going to be my products of cellular processes in the body but a lot of them are actually signals that the body sends to the brain back and forth that are they’re used to regulate these kinds of life history processes that were interested in so steroid hormones in particular are our allocating energy for super processes like reproduction or stress response of our metabolism so forth so we’re basically trying to happen to these signals so at this point usually there’s a few people wondering how it is that we managed to collect these samples you bedziesz is it’s a higher rate and this is really not that difficult because there are Orioles so we can stand underneath them and come to something false so as long as we can identify the individual in the tree that’s your name we just need to collect a very small amount towards do what a meal of urine will last do really lot of analyses and this bar scene I like because this is the heck so I’m going to talk about a bunch of different studies that try to to look at until you first looking at the interaction of energy with inceptive ability second looking at the period of lactation Alima area which is this time from a birth of an infant mother start cycling again and then also look at menopause and talk about how that regulates Tori so the first thing to note is that the physiology the mechanisms that govern ovulation and conception are remarkably similar into penn season in humans and we’ve got here are just the patterns of estrogen and progesterone during the vessel cycle there’s nothing especially we need to know about things except that if you’re not kind of scores of menstrual cycles these two these similarities between these two cycles are actually quite remarkable because these promo patterns vary quite tremendously across mammals and even across primates so apes and even share some particular characteristics but individual cycles don’t look like that most of them are messy like this is there are some cycles which feature really nice peaks in their hormones and others would show not much going on and as I arrested previously human reproductive ecologists if really try to dissect this variation and attributed much of it to variation in energies this is the sense that if you saw four again showing that weight loss leads to reduction and progesterone production curiously you can see in this particular graph then the cycle after women lost weight awesome featured of density production so we’ve been able to show very similar things with our chimpanzees looking at natural variation in food availability and what you have here are normal levels estrogen to progesterone levels for females before during and after various food abundance we get a nice bike in hormone production during the fruit abundance and you can see the reverse effects are for sure and in this craft we have estrogen levels for individual female so you can see all the individuals responding in less the same way to this change in the environment unlike the humans that you see at kind of lag even after the food shortages over if these are recovering a female

show still effect on their reproductive function and this really matters as far as their conception rates here again we have a study of humans here showing estrogen profiles in women who conceived on the top versus women who didn’t conceive so higher estrogen production matters we found the same for our chimpanzees both estrogen and progesterone are higher in conception cycles versus non conception cycles and in this case we actually had one female who conceived with really low levels of her own production that she lost your pious so this actually produces pretty strong effects on life history because it delays the waiting times inception and if we look at grapefruit proportion of the diet it’s a pretty good measure diet quality the Welsh and penzeys we find that females who are cycling dark periods of below average fruit availability tends to take much longer food cycle during good periods I miskin amount to more than a year of delay or some females we can also see the same kind of reflective and enter individual differences so in our community at cavalli we have quite a large coverage so 430 square kilometres and females tend to not gonna race that car so they stick to smaller core areas within the home range we have a group of female selected to be in the central of the southern part of the home right and another group who am in the north and this shows you our mobile rings and the distribution of the preferred fruit trees in within that home right so the center to the south has the greatest concentration of good food available whereas this females in the North our hero is not a lot to eat and we can see the correlation of that in their reproductive function of females living in that high quality area no matter what reproductive things they’re in whose higher levels of both estrogen image their infants are also far more likely to survive to reach maturity and the reproductive rates are much higher not surprisingly females when they come into a new community and try to gain access to either in this area or this area they fight pretty intensely with the resident females over for grasses to these areas and in some communities there have been females killing other females infants looking to be this kind of territorial dispute so taking these who’s all together it’s just that the chimpanzee beulah share with humans is very highly conservative approach to allocating energy towards conception that’s maybe not surprising as it turns out that the waiting time to conception for Buffy species is pretty similar so this is not a really neat of the fertility difference between species is really to be had so a better place to look then we’ll be in the period of lactation away materia because lactation is really the costliest part the reproductive cycle and it takes a lot of time so it’s also the most variable within both species so let’s look at it what’s going on there so fortunately there is a good model for humans of this process and you know it was originally thought because people still believe that the active suckling and infants what suppresses population and what regulates the birth interval and recently it’s become clear from a variety of evidence that this isn’t true it’s clear they’re women in traditional populations around the world conceived while they’re still we’re seeing their previous infants and women who are in relatively good condition like this toga woman in Argentina are able to maintain really short earth intervals despite a very intense lactation regime so these are these are former hunter-gatherers they’re not settled their sedentary they have a lot of fatty food available but they maintain a lot of the practices from when they were head together so they basically breastfeed like who’s on board what and yet they have quite short brief intervals so plenty of Elijah has studied the Toba and she proposed a new mechanism she called them out of all of Lord hypothesis Ananda here is not active sub-label suppresses fertility in it’s the cost of producing the milk relatives mother’s on energy budget so a mother in really good condition like this togo woman can afford to produce the love for her is it without taking much minutes 40 by four as an undergrad woman would really have struggle to provide that future her infant and would subsequently take longer to recover valenta user a relatively new tool in

anthropology called c-peptide of insulin and what the cpap type is it’s busy a little bit this is the whole pro insulin molecule and when it’s when s1 is actually secreted from the pancreas this epoxide is popped off and eventually is secreted into the urine so we can non-invasively measure the production of insulin in this manner and that’s exciting because insulin is one of the body’s signals and regulators of energy balance it’s also really important for allocating energy during the processes of gestation and lactations with really manages energy for mom vs energy to the baby and it’s exciting for me because this provides a mechanism are sorry a method by which we can look at energetic condition in well primates without paying so my college there were some of the first I should go out and test this method in wild Apes so here is what a playa valentien found in toba women what we’re looking at our changes in body mass and c-peptide looking from a time cycle resorption backward so at the beginning of lactation women have experienced weight loss associated with it has breastfeeding and they’re see peptide levels are accordingly quite low but as the time of cycling approaches you see that women reach a neutral than a positive energy God’s meaning they’re taking it whether they’re expecting or gaining weight and the sequence ID levels are correlated with that they’re increasing and we actually get this period of overshooting where’s the insulin production is higher than the baseline for non-pregnant long non lactating women and their explanation for this is that the ovaries have become so insulin resistant you need within a big job start here or get second going so I was able to to look at the same process in chimpanzees i took about 12 years of data on elected in female chimpanzees and around 3,000 we read samples but we basically have compiled a chart that looks very similar to what the legend you produce so again you have cycling here at the blue line and then going backward in time and you can see the same pattern of increase from a negative energy balance to more positive energy balance and you also see this overshooting period that’s very similar to what occurred in the Toba sorry oh you might just go think offices obvious that when they start lactating they just experienced a steady increase and their energy balance over the course and that’s definitely not the case lying all these up but some females are able to achieve this pattern in only about two years and those people start cycling at two years in fact the shortest birth interval we’ve had in the lowes is about two years somebody else take six years or longer in order to attain this pattern what we see is that they tend to fluctuate back and forth around neutral Jenner to negative energy balance and then over time slowly achieve at this level suggesting here is really that it’s the long period of trying to recover that positive energy balance that’s limiting the reproductive rates into pansies we’ve all sort of over able to defy meant that c-peptide levels positively predicted in both their production of estrogen and progesterone so again is to suggest that energy balance that’s regulating reproductive function and we see a compatible differences and when we look at our two groups of females the females in the relatively poor area and the northern females here had lower seek peptide levels during early lactation suggesting that this was a hard hit on her systems then for the females were in the high fall Eric’s thank yous just this two profiles of the Toba chimpanzees light up so you can see their overall similarities between them and here our lineup the x-axis to even see the difference between them and the difference is just the chimpanzees experience and watch less steep rise in their energy balance and again it’s just suggest that they’re taking much much longer to recover now we have a variety of behavioral evidence and as well as the peptide evidence that suggests that really for only about two years or females investing intensely in love production and after that it’s not having a strong effect on them so again we think it’s it’s just their ability to recover fees/costs so arte has support the human data until the only two datasets I’m aware of this kind suggest that the remedy is limited not by immersing itself by the ability to

recover a positive energy balance but along with the other day I show you this again suggests that the mechanisms that are governing enterprise intervals Inuit such amenities are very very similar and quite different species and the suggests to me that most of the difference here is not where reproductive adaptations but in the test which includes increased energy access for humans so of course humans in many societies are able to being extra calories but getting lots of meat and by cooking food which increases the colors available at food it also increases the digestibility of that food palatability particularly for young ones and across human societies we speak the turnoff provisioning which is helping the subsidized have costs of caring for an infant we also see all other kinds of food sharing between other community members and it’s also important to recognize that food flows not just to infants the close to the mother himself so even during the period that she’s exclusively breastfeeding that kid her that that cost is being subsidized by other individuals in the group and so on variety of studies have shown that having helping Kim it was a few minutes helps to improve reproductive rates and also often helps improve health and survival of those kids and as you’re seeing chinta the chimpanzees is kind of permission doesn’t happen and in fact in Japan of these males are more of a hindrance so we recently found that when we look at RC peptide levels according to grouping patters we find that females are experiencing lower energy balance winter and larger groups particularly when they’re hanging around with lots of males and this is enough as it is true of both cycling females and lactating females and this effect is strong enough to mitigate most good periods of food about buildings with lots of food lots of individuals aggregated there and if females aren’t being the kind of benefit that they might otherwise aim because they are competing for resources males and males you lots of disruptive things so we’ve done other studies to show that female corozal stress hormone levels are strongly predicted by male aggressions on males are pressing them so we move now to thinking about menopause briefly met about something that anthropologists have produced lots and lots of theory where car and it’s rarely been described as a feature that is unique to humans or is a feature that shared with many other primate species just enhanced implements and there is some captive data that as suggested that chimpanzees experience a productive premature reproductive senescence so their experience of a long post reproductive period end of this comparison is really important for the purposes of this discussion for a couple of reasons what is that menopause of course defines the end to your fertile period so if chimpanzees also have a better cause that would of course limit their fertility but another reason is that most of the adaptive hypotheses for the evolution of post reproduction in humans rely on some kind of provision from the grand pretzel generation to the young ones and since that kind of envisioning doesn’t encourage McKenzie’s the chimpanzee share feature of menopausal suggest that those hypotheses are not bad I want to point out that that defining feature of menopause is not that the reproductive system agents that’s entirely to be expected what’s different here is that the reproductive system age is such a more rapid rate within and even a bottom system so here we see steep declines in fertility at an age when other systems like cardiac capacity or full-function some arms a look at this they are try to understand age-related patterns of fertility of chimpanzees we collaborated with most of the existing field sites for chimpanzee research so this comprises probably the majority of individually recognized emails in the wild what you see here are proud of the production of offspring per female per year for different age groups the red curve is soo chimpanzee line now we’ve compared care to the akshay or a group of hunter-gatherers entire way just have to give demographic data and what you can see is the two guys you start reproducing earlier most chimpanzees have their first birth by that age 14 they don’t reach the peaks in fertility that humans do this is the reasons we’ve

already discussed that humans are maintained a much shorter birth interval but what we see is a really striking overlap in the pattern of reproductive to climb in the 40s so this might lead some people to conclude that guests humans and chimpanzees do share a feature of menopause but that’s not the correct interpretation for a really important reason here again is the same fertility carpets on red and it’s match the survivorship curve well the survivorship curve dashed line shows you are the proportion of females who are ever more who are still alive at the end of each of these age groups so for chimpanzees the main take-home point of the slide is that a reproductive rights are quite high at an age when very very few chimpanzees have still them in very good shape slip to their foods and so you see survivorship and fertility reaching zero at basically the same time this is entirely what you’d expect if the reproductive system is just aging along with everything else and there’s no premature reproductive senescence at all and we can see the contrast when we look at humans for reproduction supplies 20 at an age where even in a very marginal population forty percent of women are expected to still be alive and so this difference between fertility and survivorship comprises the post reproductive period that many many women experience we’ve also been able to go back in our chip data and we’ll get females who who are relatively healthy and just defined way whether they die soon enough I found with females who were in the relatively healthy group maintain high reproductive rates quite late in life and unhealthy females even when they were in your 20s didn’t reduce as well whereas in humans fertility will stop you can if you’re in very very good health so our data suggests that post redirected lifespan really is a uniquely human trait among primates corrosive ways to do this as well it also shows us that because of earlier reproduction in this obsidian point you can essentially have more reproductive years to spend if they could consistently live long enough and so it really here it’s the mortality patternist driving left hand fertility as much as the birth rate just lost a couple minutes talking about some future directions for our research team I’ve talked to almost entirely about this fertile period of the lifespan but we’re now now we have growing dataset or more methodologies we want to start looking at development of infants and at the aging process and well go into that too much detail I suppose show you some of the fancy new methods of producing we’re using now up parallel laser photography in order to get body size estimates of our chimpanzees i was really skeptical of how well does it work the error the error reference that we’re getting to the feeler incredibly tiny or even able to look at things like testes size using this method and we’ve also been able to use digital photography to look at dental develop any if you saw this paper my tongue except for harvard where she was able to use our photographs look at goal or eruption without ever having to capture a chimpanzee coming from a biomarker point of view i’ve recently been able to adapt a method that’s commonly used in clinics in western settings to try to evaluate muscle mass which uses creatinine and if you go to a clinic then we measure mask philosophy that collect all your here 24 hours little measure creatinine that can scale it we can’t collect your own four hours for chimpanzees about where I can take steps of samples and actually do the same thing by using a separate index and I just want to show you these are a preliminary results we can actually pick up growth curves now this is growth of skeletal muscle we can snap see in early adulthood the sexual dimorphism occurs and muscle mass between valchek bends and female chimpanzees and that we have relatively few older individuals so far you can start to see a decline in muscle mass which in humans is really one of the driving features behind the aging process this philosophy of muscle when it comes to the aging process we know almost nothing about how humans compare other ape species and most of it looks

like this it’s just mortality comparisons so this came from a paper 2001 comparing two heads and mortality rates to humans in fact our chip bags of community has mortality rates that look far more like humans because they don’t have a lot of hunting pressure and I have serious disease outbreaks now what’s interesting way to look at this is that clearly the mortality risk isn’t linear that both species are able to maintain relatively low rates more talent early told them something really extraordinary happens here where chimpanzees in their forties just die off fairly rapidly whereas humans are able to slow this process much longer we don’t even know what kills while chimpanzees in most of the cases especially the older ones and we don’t have same processes that are occurring in humans so we’re going to be doing a lot of different kinds of health analyses going to try to understand this process one of the one of the methods involves using oxidative stress this is something that I’ve worked with with my human human college degree my colleague studying humans oxidative stress is the result of damage that occurs during cellular processes and it can be documented in several ways but what is buying a a marker of DNA damage I would just been able to do a really preliminary study with chimps this is really expensive so we just did one sample for two but in humans to oxidative stress tends to accumulate with age because you you can repair the damage but that’s the expense of other life history processes if you want to reproduce you might have to cut back preparing yourselves so over time that stress tends to accumulate you see higher levels of oxidative stress in individuals who have had chronic stress who’ve been exposed to toxins or a kind of childhood diseases if that kind of thing so in our surprises we saw four females at least tentatively it kind of increased that you might expect with age what was curious with what we saw at least in some males are really high levels in early and alton and it is pattern holes with more data it’s really exciting this is the time when adult males are really investing in things like muscle mass and in competing for dominance rank and this is expected to actually be the most awesome part of their lifetime so Rawls day I can assure you that while we know a whole lot of got you in life history patterns and buys them we can gain or much better perspective on our evolutionary ideas by actually getting good data on closely related species one thing we can do is to determine which features are derived and which are shared with other Apes the influence of physiological adaptations like the ones I talked about today versus the behavioral adaptations of provisioning cooking and eventually this allows us to help evaluate the viability of all these hypotheses that are there out there and in this particular case the closer study of its processes has helped to to reveal some of the surprising similarities and differences between species so when we looked at motility because on this huge apparent difference and yet the underlying biology is very very similar and will be looked at menopause we saw on apparently similar pattern which really is functionally much different so I want to thank you for your patience and all my various flowers for this work yes you see this dress I’m assistant teacher measure to ensure us yeah well yes all those things positive stress can be measured in your observe using a bunch of different markers basically oxidative stress is the results of oxygen radicals of every story in cinemas house and the progress without just fishin so one of the ways that we can measure it is with this particular marker which is a marker of a DNA damage energy there’s one in front of that you can measure lipid peroxidation and protein degradation of thing as well this happens every one of

the measures is a little less tricky but yes yes depending on which literature you read oxidative stress is either thought to be directly or indirectly responsible for the decision process it’s either a direct reflection of the processes of aging or actively more often break down systems yes people collected data on CF hi size and composition where are you I’m not aware of the interesting to see if there was your friends cliff far as I know legend studies really the only one that’s been done in humans the reason probably because you can weigh people and so that’s probably easier way to get at it something we’re looking at in various ways in the right hands because they’re so averse to grouping that we expect that when they think they do group up there may be some interesting stuff going on and preliminary is some of the results that they’re getting our ratings are really weird so if we just look at amount of energy available per hectare we find that there’s a nice relationship with c-peptide I can expect up to a point and then all of a sudden at least for males at the highest fruit availability they’re experiencing really low energy balance they’re doing something in one of your earlier slides you showed different reproductive rates for chimpanzees in different habitats locations and I’m under the tie forest ones have particularly low rates it looked like yeah cuz might well it might like my question really busu might have been higher what is higher than tie if i recall correctly but my question is I remember that you have more male female associations and tie because of the high leopard predation rates there on a flat stole the case but certainly it’s been published do you see that as the link basically there then or or army is it would it be interacting with you know food quality or availability I don’t know a lot about the quality of food available at time I think it probably difference between different study sites but I’ve acident that’s really amazing idea they’re forced to maintain hired bruce and that may be as possible they did another assume there’s some other strange things for the results will i suggest that they transition between lactation and cycling earlier and just enough cycling for much much longer in east african chimpanzees so the invar of them was right that much different but that transition has moved almost to the vanilla have you started thinking about are investigating the allocation of resources for these females that are in these stress conditions sex differences in allocations so when you look at their so their reproductive rate is lower their survival of kids is lower is there a difference between sons and daughters survival and um with it you know they don’t reproduce often enough for us to notice from the real challenges is that so many females had birthday was a nine 10 years so we we have a difficult time doing anything compared with their kids but that’s certainly something we’re thinking about our development projects and one of my key interests in that project is understand the importance of maternal energy on the development of the infants and not only using those kind of lactation c-peptide 80 we can take that look now it’s five years we can look at those kids and see how they’ve to God but also using those neighborhood using rank as well and we’ll be looking at aspects of social development things like distance from the mother however they play a role they can play as well as the morphological development because I think it I think it was a rang a tang data where they did the sea peptides and showed that the energetic status of the mom during the development actually affected whether they would turn out to be Peter Pan males versus full flip flanged males you know yeah we just sudden brother I pass as anybody yeah sure a lot of I think you’re too

there average so No so that’s amore like 70 million regular and then by the time the foremost them gone yeah so we don’t there’s been one really nice study recently of menopause looking at eggs in two phases that diagn actually in Susan’s facilities and they took sessions in the river count you know the number of follicles that are left and compare that to humans it looks 38 a very much supports the data that I after a while suggesting that their females are still reproductive them in foil as far as the amount of energy it takes to do 70 eggs or how many they start off with you mentioned this data showing the human and chimpanzee email geez like several men terms of its regulation by their Jenna physicians and you mentioned that that was different than what we see in other species generations of all profits um some of you know predator are interesting because they’re so very and they go from species that reliably reviews every time they have an opportunity look I don’t think person and so many more species stuff and so there seems to be the filter is not on conception but on survivorship and they tend to give birth in a period when there’s lots of food available and that makes sense if you’ve got a small kid that’s keep her up in gravity because then you take advantage what make you food and have a good chance of making it that doesn’t come but humans and apes and probably some of the other large primate species show a much different pattern where there there’s a more of a filter our conception this is where we start to see there are relatively few species baboons where a key an ace that we don’t often cycle repeatedly before conceiving and then there’s a flip side of that is that their infants seem to have a much higher probability of surviving so in other mammals you would see this kind of contrast being an income rating Apple breeding so lemurs are relying on income on the grease the baby and apes are relying on having a capital of France it’s not really true in fact you were finally looking for except most primates are ankle readers in terms of winning time they’re babies what most parents are avid readers in the sense that they are sensitive to bilities so even in a lemur if they’re in really poor condition things just scare the breeding season so it’s it’s a it’s a different pattern that doesn’t have to my knowledge ok I’m going more yeah we’ve been talking about this in our little evolutionary development a little discussion group about this this mystery of why humans despite the fact that they can get down to really starvation levels and continue to cycle do you see that in other primates and what what what yeah what’s your ideas of that um so in chimpanzees we certainly see a lot of gaps when the food is Ellen we will stop cycling and pick up a gallon and think we have the enemy think we know they didn’t even lose it I think they just stop debating it suddenly happens in humans but but you’re right then they seem to tolerate how much tolerate a lot of men of their stress is still cycle but then the kind of work that PR else it’s done is really showing that a lot of those cycles are free for they have a pretty low likelihood of conception so even a cycle that has best ratio we normally have a gauge that kind of thing

may have a briefly low-light ovulate or they’re being an adequate individual and implantation to occur these reproductive hormones even affect the ability of the O going to be fertilized so there’s a huge amount of variation that we just can’t see without actually looking at profiles we get our spicy adolescent females as well cycle repeatedly do they believe it or not so you just have a movie low likelihood of getting pregnant