The Evolutionary Biology of Extinct and Extant Organisms

By Subir Ranjan Kundu

The Evolutionary Biology of Extinct and Extant Organisms offers a thorough and detailed narration of the journey of biological evolution and its major transitional links to the biological world, which began with paleontological exploration of extinct organisms and now carries on with reviews of phylogenomic footprint reviews of extant, living fossils. This book moves through the defining evolutionary stepping stones starting with the evolutionary changes in prokaryotic, aquatic organisms over 4 billion years ago to the emergence of the modern human species in Earth’s Anthropocene.

The book begins with an overview of the processes of evolutionary fitness, the epicenter of the principles of evolutionary biology. Whether through natural or experimental occurrence, evolutionary fitness has been found to be the cardinal instance of evolutionary links in an organism between its ancestral and contemporary states. The book then goes on to detail evolutionary trails and lineages of groups of organisms including mammalians, reptilians, and various fish. The final section of the book provides a look back at the evolutionary journey of "nonliving" or extinct organisms, versus the modern-day transition to "living" or extant organisms.

The Evolutionary Biology of Extinct and Extant Organisms is the ideal resource for any researcher or advanced student in evolutionary studies, ranging from evolutionary biology to general life sciences.

• Provides an updated compendium of evolution research history
• Details the evolution trails of organisms, including mammals, reptiles, arthropods, annelids, mollusks, protozoa, and more
• Offers an accessible and easy-to-read presentation of complex, in-depth evolutionary biology facts and theories

• Language: English
• Publisher: Academic Press
• Release date: Mar 23, 2021
• ISBN: 9780128232835

Subir Ranjan Kundu

Dr. Subir R. Kundu is a senior researcher conducting extensive studies on “in situ” conservation models at the University of Calcutta in Kolkata, India. Previously, he was a senior research fellow at the Acharya Jagadish Chandra Bose Indian Botanic Gardens under the Botanical Survey of India in Howrah, India. Dr. Kundu received his MSc. in botany from Kanpur University, Kanpur India, specializing in cytogenics and plant breeding; he then received his Ph.D. in botany from the University of Calcutta, specializing in plant geography, systematic botany, and conservation biology. He is the author of four botany and conservation-related books and numerous journal publications on conservation and evolutionary biology.

Book preview

The Evolutionary Biology of Extinct and Extant Organisms

Subir Ranjan Kundu

Edited by

Sofia Naznim

Table of Contents

Cover image

Title page

Copyright

Preface

Acknowledgments

Introduction: Missing link: When an outmoded term holds in-between features between the ancestors and its descendants

Chapter 1. The transitional features of missing link illuminate the molecular nuts and bolts of biological evolution

Chapter 2. If and when evolution is the ultimate essence of life: what is the evolutionary identity of the missing link (resembling Archaeopteryx)

Chapter 3. Walking with Cynodont to explore the uncharted evolutionary trail of mammalian lineage diverged out of reptilian

Chapter 4. One small step for amphibious fish, one evolutionary leap for moving tetrapods on Earth

Chapter 5. Evolutionary origin of amniotic egg: the transitional form between amphibians and reptiles in the doubt clear session

Chapter 6. When contemporary discoveries pushes the bony fish to ancestral or evolutionary back seat and discreetly pushes cartilaginous fish in the advanced or front seat

Chapter 7. Hemichordates: the bilaterians lineage (also known as phylum- Deuterostome) in the evolutionary crossroads of developmental biology

Chapter 8. Cambrian evolution of Onychophorans: in the evolutionary labyrinth of Arthropods, Annelids, and Molluscs

Chapter 9. The extent of Ctenophore uniqueness—distinctly recognized to be quasi-Cnidarians or stunted Bilaterians

Chapter 10. The Protistan link in transition: down the evolutionary trail from unicellular Protozoa to multicellular Metazoa

Chapter 11. Evolutionary mysticism of Euglena: a sagacious soul of a plant in the body of an animal

Chapter 12. Virus: a stepping stone in transition in the course of evolutionary journey from the world of nonliving to the world of living entity

Chapter 13. Once there was an ancestor between humans and apes: in the quest for the enigmatic missing link

Chapter 14. Mitochondrial Eve and Y-chromosomal Adam on planet Earth: Humanity’s metaphoric missing-link between prehistoric past and contemporary present

Conclusion: Missing link: In search of our distant cousins footprints, a quest for our evolutionary journey to the past

References

Index

Copyright

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Preface

This book is the creation of a dedicated and determined effort by a single and experienced author on the topic of evolutionary links of living things. It primarily emphasizes the biological evolution of major groups of organisms in the backdrop of a diverse array of hypothetical examples to match with a distinct biological set of evidence that testifies to our understanding of major evolutionary developmental transitions, specifically over the last four decades. This book is an earnest attempt to present the critically reviewed unique progress of biological evolution via the advancement of genomics/molecular footprints that have made significant contributions in the past two decades and continue to play a key role in our better understanding of evolutionary progress in the current environmental scenario. The work of the author will advance our knowledge and provide a source of valuable information. I have no doubt that this is a significant contribution to research in the field that would be of substantial interest and relevance to a large proportion of the readership.

I had the opportunity to read the book written by Subir Ranjan Kundu with a great deal of interest. In the first part of the book, the author has critically reviewed and exclusively synthesized data with supporting shreds of evidence on the lack of information and how the recent significant fossil finds have also added greatly to our understanding of several major clades and transitions. At the end of this book, an earnest endeavor has been made to depict the evolutionary journey of microscopic organisms by highlighting the important points as a strong set of evidence, though key occurrences of evolutionary transition are still puzzling. Readers would surely be enthralled to enjoy the remaining chapters in the middle, as those chapters would be equally interesting to hold their attention and walk them through the trail of evolutionary transitions.

This book is for all (graduate and postgraduate students, researchers, and inquisitive heterogeneous readers) who are interested in biological evolution, and I do believe that it might serve as a sourcebook for review and for understanding the scientific concepts of biological evolution in transition in a simplified manner for curious learners even from nonscientific communities. The book is written to help clearly understand and access either parts of or much of the whole of evolutionary theory as required by the reader.

I hope this book will give us the opportunity to address important knowledge gaps and research. I also believe that it will definitely provide evolutionary biologists with an alternative way to explore and decipher evolutionary mysteries of large macroscopic, tiny microscopic, and transitional forms of prehistoric organisms in between with fascinating structural formation by undertaking phylogenomic investigations.

Dr. Sundar, S.

Scientist

S.S.Research Foundation

130/123 Veerappa Puram Street

Kallidaikurichi, Tamil Nadu

PIN-627416

India

Tel: [phone]

E-mail: [e-mail]

Acknowledgments

I express my deep sense of gratitude and indebtedness to Dr. Rafal Kuczewski, Deputy Director, National Park of Wielkopolska, Mosina, Poland; Dr. Mohaned Shebl, Faculty of Agriculture, Suez Canal University, Ismailia, Egypt; Dr. Nikunj Bhatt, Associate Professor in Zoology, VP & RPTP Science College, Gujarat, India; Mr. Bipul Chakrabarty, Director, Tata Steel Zoological Society, Jamshedpur, and Former Scientific Officer, Central Zoo Authority, Ministry of Environment, Forests and Climate Change, and the Government of India for their suggestions and guidance in this present writing.

I am especially pleased to acknowledge Dr. Pradipta Kumar Sarangi, Lecturer, Department of Zoology, Indira Gandhi Memorial College, Odisha, India; Mr. Rogier van Rossem, Board of Directors, Projects and Programs Coordinator, King Cobra Conservancy, USA; Mr. Patrick Comins, Executive Director, the Connecticut Audubon Society, Fairfield, USA; and Mr. Anirban Roy, Senior Scientific Officer, SAFE-South Asian Forum for Environment, Kolkata, India, who helped me in drafting the different parts of the manuscript that required reviewing consultations of literature, library consultations, discussions, etc.

I am thankful to Susan Zadek and Sung-Min Han, Albert Campbell Library, and Eva Lew, Bloor Gladstone Library, Toronto Public Library Network, Toronto, Canada, for extending library facilities and providing necessary help in locating literature required for this project to be completed.

I am also thankful to Ms. Sashi Sinha and Mr. Goutam Saha, freelance graphics artists from Kolkata, India, for preparing the graphical presentation of this book.

I express my gratitude and thank all academicians, editors, publishers of books and journals, and colleagues for sharing the printed and digital materials, providing valuable suggestions, tendering necessary clarifications during the past few years, and for selflessly helping me out to complete this task.

Introduction: Missing link: When an outmoded term holds in-between features between the ancestors and its descendants

Man appears to be

the missing link

Between anthropoid apes

and human beings

—Konrad Lorenz

The sudden shouting of my fellow passengers woke me up from my half-asleep state on the day I got stranded in the Hong Kong International Airport, as the flight operations had been put on hold for an indefinite period of time due to the emergency situation immediately after the devastating fallout of the earthquake and the scary aftermath of tsunamis on the Christmas of 2004. I still recognize that natural disaster as the worst, most dreadful experience in my life, as I did not have much choice but to witness an insurmountable human misery and mass losses of human life in the tsunami-affected countries across South and Southeast Asia. When I got stranded in the transit lounge of Hong Kong for almost 17 hours, after traveling from Toronto for more than 15 hours of nonstop flight, I was exhausted due to jet lag. I was anxiously looking for the information about the departure schedule of the connecting flight to Calcutta to meet my ailing father. I did not remember precisely how long I waited in the transit lounge for the connecting flight to reach Calcutta, which was only around a 4-hour flight from Hong Kong. I only remembered that I started my journey in the late afternoon of Christmas 2004, and I reached Calcutta, my parental home, between the end of December 28 and the beginning of December 29, 2004, after an exhausting, prolonged journey and the dreadful episode that was difficult for anyone to ever forget.

People from the northern hemisphere would definitely understand how difficult it is to secure an airplane ticket in Europe and North America during Christmas time. Most of the office establishments and travel agencies remained closed, and hardly anyone could get in touch with any friends and acquaintances during this time of the year. Either they are away from their working places or on a planned vacation to spend time with family and friends. On my way back home from my workplace, I got a telegram (which is apparently a missing link in the arena of conventional communication in India since 2014 and gradually made obsolete in different parts of North America a little earlier than 2014), which clearly mentioned four words Father ill, come home, dated December 24, 2004. After going through the telegraphic message, it seemed to be an impossible task for me to secure a flight ticket on the next day. But I kept on trying with different travel agencies across Toronto and the Greater Toronto area from west-end Kipling to east-end Scarborough to secure a confirmed airplane ticket to see my father, who had suffered from a severe brain hemorrhage. Eventually, one of the travel agents finally informed me of the booking confirmation from Toronto to Calcutta via Hong Kong just 7 hours before traveling, which I considered to be an experience like winning a jackpot after I had gone through an intensive period of anxiousness. I did not know at that time I would face such a difficult moment in my life, full of dreadful memories. After traversing around 7,802 miles from Toronto to Hong Kong in a nonstop 15-and-half-hour flight, I tried to lie on a cozy seat at the Hong Kong Airport to stretch out my legs and arms and wait for connecting flights to Calcutta. As most of the passengers on the flight I traveled with were of Chinese origin, Hong Kong was the final destination for most of them, whereas the rest of the passengers were taking connecting flights to different parts of China or its neighboring countries of East Asia and far East, Singapore, Indonesia, Laos, Japan, Mongolia, etc. I still remember the devastating news I received after getting into the transit lounge, which still gives me goosebumps to this day, that a severe earthquake (a magnitude of around 9.1 on Richter scale) had triggered in the epicenter of Indonesia and extended Sumatra to Andaman in the Indian Ocean region, leading to a series of tsunamis that hit and washed away a vast array of sea-coastal regions of 14 countries around the Indian Ocean. The occurrence of such an unexpected natural disaster created an almost warlike emergency situation, resulting in the cancellation and further delaying of most of the flights that were scheduled to be flown out of the Hong Kong International Airport till the situation became stable for flight operations.

Having to wait for an indefinite period of time, I did not have many options and there were only a few things to do. I kept on drinking the same black coffee and helplessly watched the news on the giant-sized LCD screens telecasted by different news channels including BBC, CNN, and ATN and witnessed the worst part of the human loss caused by the cascading effect of natural calamities, the unforgettable earthquake, and series of tsunamis which took around 230,000 lives in 2004. I waited impatiently for the connecting flight and checked the display boards with the arrival and departure schedule of all flights every half hour. As the information desk was closed, the stranded passengers like me kept asking the same questions and vented their frustration to a few airport personnel at the information desk. I remembered that while I waited for the connecting flight I was trying to explore the metaphoric resemblance between me and Viktor Navorski, the main character of the movie The Terminal, who gets stranded in the Terminal 1 of an airport for an indefinite period of time. I still remember the movie vividly, as I watched it when it was released earlier that year. The movie was directed by one of my favorite directors Steven Spielberg, partly inspired by a real-life incident of an Iranian citizen, Mehran Karimi Nasseri, who got stranded in the Terminal 1 of Charle de Gaulle, Paris, France, for 18 years.

In reality, my situation was not as bad as in the movie, as I was only stranded for 17 hours. But I realized that on a journey, any biological entity has to be stranded in transit for an indefinite period of time. Like any other accident, the earthquake and tsunamis created a situation where most people would not define their journey as progressing toward their destinations in terms of change of their life journey progress in spatiotemporal scale. As the clock tick-tocked and remained working, an apparent movement of the life had remained standstill during the post-tsunami disaster regime. Hence, it is difficult sometimes to narrate this phase of the journey of life in the backdrop of spatiotemporal changes, driven by an unexpected and unleashed vortex of the natural disaster.

My journey during Christmas time in 2004 and the experience of being stranded in the transit lounge for connecting link was a metaphoric journey of life experiencing devastation in the middle of desolate, deserted, war-torn battlefields, where the mode of the voluntary journey of life has unexpectedly been changed to the mode of involuntary journey amid the chaotic ambiance of devastation, helplessness, tears, and death. Apparently, the gravity of those natural calamities left me dumbstruck to lie on a chair in the transit lounge where time ticked on through the X-axis, but no spatial movement was found to be in a functional state in the Y- axis, and my fatigued brain could not properly figure out whether I was really waiting for a connecting link or if state as a mere instance of entity with missing link left me stuck helplessly in the labyrinth of emotional upheaval.

However, to elucidate the concept of missing link and connecting link in real life and to provide a better understanding of its integration to the journey of evolution, let us consider a socioeconomic example, an effort to establish the missing link between two distinct segments in human society: poor and rich people. According to the contemporary Western concept, money is the missing link between these two socioeconomic segments of society, as money could make our present life wealthy and ensure our prosperous future; this money seems to be the ultimate wealth that could make our life happy. Apparently, it seems that there is a linear relationship between the missing links of wealth and happiness. Is that kind of relationship found to be linear always in real life? Let us find out whether rich people are always happier than poorer ones or otherwise.

From the psychological perspectives, the two famous psychologists Ed Diener and Robert Biswas-Diener (2008) have mentioned in their book entitled Happiness: Unlocking the Mysteries of Psychological Wealth, that It seems natural to assume that the rich people will be happier than others, further stating that money is only one part of psychological wealth, so the picture is complicated. The authors agreed that there is apparently no doubt that rich people and developed nations are happier than poor people and developing nations, but they have contemplated that money as financial capital is not strong or powerful enough to secure happiness. From the psychological perspective, they considered that fulfillment of the prime necessities of life by availability of food, clothing, and dwelling place would make people happy in a way that enhancement of the disposable income would hardly impact the sense of well-being of the people. As an example, the family income of a four-member family in Canada can be considered poor in terms of the financial scale if the net annual earnings of that family were $44,266 or less in the financial year of 2018-19. Consequently, a supplementary grant of $6,000 would really bring a sense of happiness among the family members living below the poverty line. On the other hand, the same grant for the family of the same size with a net annual income of $150,000 has little impact on their enhancement of well-being.

J.D. Roth (2010), one of the famous financial analysts and eminent economists of North America, has mentioned in his book entitled Your Money: the Missing Manual that the life-changing potential of money is found to be a one-sided story, as the unlimited influx of money to any needy person might be proven to have a substantially negative impact if the concerned person could not maintain a balance between earning and spending or did not maintain a sustainable living between too much wealth and too little wealth.

Seemingly, more spending eased our life, as we could achieve our dream of living by spending money. But then, is that true in real life? In a recent personal finance publication, entitled Your Money or Your Life, Vicky Robins and Dominguez (2008) have contemplated that the relationship between a spending spree and happiness is found to be nonlinear. That means that spending money on impulsive buying would make us a little more unhappy than our earlier state and that overspending without setting any well-adapted social goal could drag anyone into the debt-strapped condition and a more unhappy state.

To be happy, a sense of freedom needs to be nurtured, which could be ensured by exploring and culminating social values, social relationships, proper utilization of wealth to achieve social goals, and achieving sustainability and development in the socioeconomic arena. The missing link between unhappy and happy people in society is found to be related to the utilization of these abstract forms of values, apparently invisible, which are popularly considered as social capital. Hence, the recognition of financial capital might be apparently considered a valid currency, the transcending of which from one end to the other would transform social status from poor to rich or vice versa, But the ultimate missing link, social capital, rather than financial capital needs to be recognized as it has unbound potential in driving the social and socioeconomic evolution in our society.

The term missing link is a media-friendly term that has frequently been used in contemporary scientific literature (mainly in literature related to physical anthropology) as an effort to build an evolutionary bridge between the lower group of primates and apes and between apes and modern human species. In a number of situations in the scientific world, particularly in the world of biology, this terminology has been used without understanding its deep-rooted ramifications. Technically, the term missing link explicates the transitional morphologies or forms of the paleontological evidence discovered, which possess a number of common features that evolutionists and evolutionary biologists would scientifically establish as an evolutionary relationship between the extinct form of organisms and its likelihood-derived living successor, the extant form of the organism. Therefore the missing link shows the possession of a set of features in transition of the ancestral organism, evolved with a set of derived traits found in its descendants that are supposedly evolved from those erstwhile predecessors. Apparently, the term missing link was not an unusual or unknown term to Charles Darwin, the father of biological evolution, as his mentor, Charles Lyell, used this term in 1851 whenever he had been engaged in paleontological studies, in particular studying transitional fossil specimens to establish evolutionary relationships between extinct and extant. Yet, Darwin had put aside this terminology and did not use it in his work.

On November 24, 1859, after the publication of The Origin of Species by Means of Natural Selection, the bible of biological evolution, Charles Darwin was invariably convinced that his monolithic doctrine on biological evolution must be effectively substantiated by the future discoveries of paleontological evidence in transition (i.e., transitional fossil evidence between two distinct forms of species) between small primates and modern human species. But the terminology missing link is surprisingly missing from his bible of biological evolution.

In 1861, Alfred Wagner discovered a transitional fossil between reptiles and avians, called Archaeopteryx (which means ancient wing), from the limestone deposit of Solnhofen, Germany, which evolved around 150–40 million years ago (MYA) in the Jurassic Period (Howells, 2011). It was quite surprising that such an important observation was missing from Darwin's work; nevertheless, he received a scientific communication, dated January 3, 1863, from a renowned paleontologist, Hugh Falconer, who studied meticulously the fossil of Archaeopteryx of the Jurassic era, which had composite features of birds and reptiles: possession of feathers, claws, teeth, and bony tails (Black, 2018). When the presence of feathers encouraged a group of scientists to consider Archaeopteryx as a Jurassic bird, the presence of Saurian traits (dinosaurs) made another group of scientists consider it of reptilian origin. Nowadays, the world of science still recognizes Archaeopteryx as a missing link between birds and dinosaurs, though a detailed molecular investigation needs to be done to substantiate the paleontological evidence. According to Nicholas Pyenson, the current curator of marine mammal fossils, the Smithsonian Museum of Natural History has argued that most likely Darwin has tried not to use the term missing link consciously in his doctrine of evolution, and Nicholas Pyenson has further argued that Life is a tree, not a chain (Black, 2018).

Technically, it is clear that missing link is the transitional form of the fossilized remnant of any organism that helps to build an evolutionary bridge between a phylogenetically related extinct organism and its extant descendants; for example, Archaeopteryx acts like a missing link between the extinct group of reptiles, the dinosaurs, and the modern-day extant group of birds. From a logical perspective of evolution, there is no difference between missing link and connecting link, as connecting link plays the same cardinal role as a missing link, establishing an evolutionary bridge between the organisms belonging to the two distinct taxonomic groups, which are phylogenetically adjacent to each other. Although both forms of evolutionary bridges have played the same role to elucidate the evolutionary succession of evolutionary tracking from its ancestral form to the contemporary descendants when missing links represent the transitional extinct forms or fossils of any organism, the connecting links are the living ones, sometimes alternately recognized as living fossils. For example, the duck-billed platypus or Ornithorhynchus is found to be the transitional living form between reptiles and mammals.

Let us review the interpretation of Briana Pobiner, the paleoanthropologist in charge of the Smithsonian Human Origins Program, who has defined missing link as: To me, the idea of a ‘missing link’ implies a template of ‘family chain’, a unidirectional linear chain of one species evolving into another, evolving into another, and so on (Black, 2018). Briana Pobiner has further clarified that biological evolution does not fit into the stereotypical perception of missing link, as she defined biological evolution as a metaphoric family-tree that produces a diverging treelike branch with multiple descendants of an ancestor species existing at the same time, and sometimes even alongside that ancestor species (Black, 2018). It has further been clarified by paleoanthropologists that the linear chain-like model of evolutionary interpretation has an obsolete perception as evolutionary progress has followed the path of the reticulate pattern of advancement in terms of spatiotemporal divergence and mode of diversification from ancestral lineage to emerge in a derived form after traversing down the long evolutionary trail. This results in the logical emergence of paleontological evidence or fossil evidence that has difficulties being assigned to a certain category or form, which could directly indicate its phylogenetic success, where the emergence of the extant member supposedly descended from its erstwhile ancestor.

As a matter of fact, the history of biological evolution has gone through an evolutionary meshwork of a spatiotemporal trail, where the species did not have any other choice but to adapt to the dynamic changes of environment and tune in on its process of diversification and migration to survive in a favorable environment. On its way to the evolutionary journey, a number of species with their ancestral traits have been pushed into extinction by their descendants or have become extinct when they were not flexible enough to cope with a changing environment. So, it is apparently reasonable that the long trail of biological evolution of any organism must have innumerable patches of missing links, the unavailability of which poses a serious challenge to paleontologists, evolutionists, and evolutionary biologists who wish to sketch out an undisputed, unanimous blueprint of evolution, without being involved in scientific bickering and counter-bickering of observations, interpretations, and explanations to solve the puzzle of evolution.

In this regard, the theoretical perception of the missing link of the eminent paleoanthropologist, John Hawks, at the University of Wisconsin, Madison, USA, needs to be shared. He firmly stated: Missing link is an outmoded term in biology, which I have to say most of us think it should be forgotten and never used, and he further said: On the one hand, it's a truism we can never recover every individual that contributed genetically to today's species, so we should expect ‘links’ to be missing. On the other hand, it implies total ignorance, where we usually know quite a lot about transitional forms (Melina, 2010). In support of further elucidation of the reticulate pattern of evolution, rather than the linear, straight-line one, John Hawks stated: Probably the most important thing is that most of the fossils we find aren't actually links (Melina, 2010). He further stated: The number of extinct side-branches is much larger than the number of true genealogical connections in the fossil record, and so when we find a fossil, we don't assume it's an ancestor of anything, we interpret it as a sister group of somethings (Melina, 2010).

Ian Tattersall, one of the well-known academic and famous North American paleoanthropologists, and curator of the American Museum of Natural History, New York, USA, is found to be less critical about using the term missing link as he believes that the term missing link itself is a bewildering terminology in terms of improper interpretation of a biological term. In support of his explanation on this particular term, Ian Tattersall stated: The notion of the ‘missing link’ dates from the early 20th century when it was thought that human ancestors formed a sort of single-chain receding into the remotest past, and he further stated with firm affirmation: We now know that the picture was much more complex than that, with a lot of now-extinct species jostling for ecological space and evolutionary success (Melina, 2010).

With respect to its application, there is no technical difference between the terms missing links and connecting links, and both apparently seem to be two sides of the same coin as they are both used to elucidate the establishments of phylogenetic relationships between two taxonomically or phylogenetically distinct evolutionary groups. There is a clear visual distinction that missing links represent the transitional fossils (without life) on the ancient type, whereas connecting links represent the living fossils (extant entities but possessing erstwhile ancestral traits) that follow the cascade of a life cycle. Perceptually, there is a subtle difference between missing links and connecting links: the difference between the Aristotelian interpretation of potentiality and actuality. When paleontologists work together with interdisciplinary scientists to decipher the phylogenetic encryption of extinct forms of paleontological evidence to get closer to its ancients and establish its phylogenetic relationships with its descendants, scientists need to go through a reticulate meshwork of interpolation and extrapolations.

In studying the missing link evidence, there was a minor problem that paleontologists and evolutionary biologists often used to face because they would not have the opportunity to study the entire life cycle of the concerned organism (as the fossil is normally found to be available in a particular form of life in a certain point of time of the life cycle of the organism). Sometimes, phylogenetic interpretations that are solely based on paleontological studies would not go above and beyond biased observation and/or interpretation of observation to refer to the missing link as a metaphoric cousin of a particular organism, which belonged to an evolutionary group, when it could have been interpreted as a metaphoric parent of the concerned organism, or might have been phylogenetically distant in relation. Hence, the phylogenetic interpretation of the missing link seems to be more tenable to interpret when exploring the uncharted territory as well as a potential-guided expedition process, where the personal level of observation and interpretation of observation could alter the final inference of the progress of the evolution of any organism. While the connecting link is much more an actual-driven exploration, where scientists have a chance to study the physiological/morphological changes of the connecting link (the living fossil) to correlate it to the two phylogenetically distinct, extant, evolutionary groups, the chances of biased observation and interpretations are less likely.

The imposition of pseudoscientific acquisition of using the term missing link has been stigmatized with random usage or portrayal of an imaginary picture of apes in biology textbooks, which has some visible resemblance to chimpanzees on the one hand and resembles part of some features found predominantly in modern human species on the other hand. Presentation of such a picture a the textbook as a missing link creates a buzz among creationists and antievolutionists who may raise their voice and try to influence students even at secondary level to disbelieve and accept the scientific evolutionary interpretation of origin and evolution of modern human species in the course of time (which took millions of years). However, contemporary elucidation of the history of the origin and evolution of modern human species by anthropologists, paleontologists, evolutionary biologists, and genomicists revealed that the chimpanzee, one of our evolutionary close relatives, diverged out of the ancestral anthropogenic rootstock around 3.6 MYA and we, the modern human species, phylogenetically split out of the hominid rootstock around 6 MYA (Black, 2018).

If it is one side of reality that our genome is the evolutionary holy grail of our origin and evolution, the other side of the reality of narrating the history of origin and evolution of modern human species would remain incomplete without extensive studies of the vast array of collections of our transitional fossils (comprising fossils of hominoids and hominids), and this prompts us to use the term, which most of us dislike to use, missing link. Well, it is not necessary to utter a term that sounds pseudoscientific or scientifically incorrect, but there is nothing wrong in accepting reality by referring to it as transitional form or intermediate form. Without acknowledging the evolutionary importance of those links in transition (whether be recognized as connective links or evolutionary